Remove support and tests for HSTS priming from the tree. Fixes #384

56 files changed, 26 insertions, 1812 deletions

diff --git a/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js b/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js
index ff4157a3b..eb77bc158 100644
--- a/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js
+++ b/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js
@@ -61,8 +61,6 @@ function pushPrefEnv() {
     "set": [
       ["security.mixed_content.block_active_content", true],
       ["security.mixed_content.block_display_content", true],
-      ["security.mixed_content.use_hsts", false],
-      ["security.mixed_content.send_hsts_priming", false],
     ]
   };
   SpecialPowers.pushPrefEnv(options, deferred.resolve);
diff --git a/devtools/client/webconsole/test/browser_webconsole_bug_632817.js b/devtools/client/webconsole/test/browser_webconsole_bug_632817.js
index 561e3b112..dc976411f 100644
--- a/devtools/client/webconsole/test/browser_webconsole_bug_632817.js
+++ b/devtools/client/webconsole/test/browser_webconsole_bug_632817.js
@@ -95,10 +95,6 @@ function testXhrWarn() {
 
   let lastRequest = yield waitForFinishedRequest(XHR_WARN_REQUEST_PREDICATE);
   if (lastRequest.request.method == "HEAD") {
-    // in non-e10s, we get the HEAD request that priming sends, so make sure
-    // a priming request should be sent, and then get the actual request
-    is(Services.prefs.getBoolPref("security.mixed_content.send_hsts_priming"),
-        true, "Found HSTS Priming Request");
     lastRequest = yield waitForFinishedRequest(XHR_WARN_REQUEST_PREDICATE);
   }
 
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index b3e26da33..8eca47495 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -9961,27 +9961,6 @@ nsDocShell::InternalLoad(nsIURI* aURI,
 
       return NS_ERROR_CONTENT_BLOCKED;
     }
-
-    // If HSTS priming was set by nsMixedContentBlocker::ShouldLoad, and we
-    // would block due to mixed content, go ahead and block here. If we try to
-    // proceed with priming, we will error out later on.
-    nsCOMPtr<nsIDocShell> docShell = NS_CP_GetDocShellFromContext(requestingContext);
-    // When loading toplevel windows, requestingContext can be null.  We don't
-    // really care about HSTS in that situation, though; loads in toplevel
-    // windows should all be browser UI.
-    if (docShell) {
-      nsIDocument* document = docShell->GetDocument();
-      NS_ENSURE_TRUE(document, NS_OK);
-
-      HSTSPrimingState state = document->GetHSTSPrimingStateForLocation(aURI);
-      if (state == HSTSPrimingState::eHSTS_PRIMING_BLOCK) {
-        // HSTS Priming currently disabled for InternalLoad, so we need to clear
-        // the location that was added by nsMixedContentBlocker::ShouldLoad
-        // Bug 1269815 will address images loaded via InternalLoad
-        document->ClearHSTSPrimingLocation(aURI);
-        return NS_ERROR_CONTENT_BLOCKED;
-      }
-    }
   }
 
   nsCOMPtr<nsIPrincipal> principalToInherit = aPrincipalToInherit;
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index 1e0c9562e..7a73fae71 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -18,11 +18,11 @@
 #include "nsINode.h"                     // for base class
 #include "nsIScriptGlobalObject.h"       // for member (in nsCOMPtr)
 #include "nsIServiceManager.h"
+#include "nsIURI.h"                      // for use in inline functions
 #include "nsIUUIDGenerator.h"
 #include "nsPIDOMWindow.h"               // for use in inline functions
 #include "nsPropertyTable.h"             // for member
-#include "nsDataHashtable.h"             // for member
-#include "nsURIHashKey.h"                // for member
+#include "nsTHashtable.h"                // for member
 #include "mozilla/net/ReferrerPolicy.h"  // for member
 #include "nsWeakReference.h"
 #include "mozilla/UseCounter.h"
@@ -182,13 +182,6 @@ enum DocumentFlavor {
   DocumentFlavorPlain, // Just a Document
 };
 
-// Enum for HSTS priming states
-enum class HSTSPrimingState {
-  eNO_HSTS_PRIMING = 0,    // don't do HSTS Priming
-  eHSTS_PRIMING_ALLOW = 1, // if HSTS priming fails, allow the load to proceed
-  eHSTS_PRIMING_BLOCK = 2  // if HSTS priming fails, block the load
-};
-
 // Document states
 
 // RTL locale: specific to the XUL localedir attribute
@@ -406,34 +399,6 @@ public:
   }
 
   /**
-   * Check to see if a subresource we want to load requires HSTS priming
-   * to be done.
-   */
-  HSTSPrimingState GetHSTSPrimingStateForLocation(nsIURI* aContentLocation) const
-  {
-    HSTSPrimingState state;
-    if (mHSTSPrimingURIList.Get(aContentLocation, &state)) {
-      return state;
-    }
-    return HSTSPrimingState::eNO_HSTS_PRIMING;
-  }
-
-  /**
-   * Add a subresource to the HSTS priming list. If this URI is
-   * not in the HSTS cache, it will trigger an HSTS priming request
-   * when we try to load it.
-   */
-  void AddHSTSPrimingLocation(nsIURI* aContentLocation, HSTSPrimingState aState)
-  {
-    mHSTSPrimingURIList.Put(aContentLocation, aState);
-  }
-
-  void ClearHSTSPrimingLocation(nsIURI* aContentLocation)
-  {
-    mHSTSPrimingURIList.Remove(aContentLocation);
-  }
-
-  /**
    * Set the principal responsible for this document.
    */
   virtual void SetPrincipal(nsIPrincipal *aPrincipal) = 0;
@@ -2987,11 +2952,6 @@ protected:
   bool mUpgradeInsecureRequests;
   bool mUpgradeInsecurePreloads;
 
-  // if nsMixedContentBlocker requires sending an HSTS priming request,
-  // temporarily store that in the document so that it can be propogated to the
-  // LoadInfo and eventually the HTTP Channel
-  nsDataHashtable<nsURIHashKey, HSTSPrimingState> mHSTSPrimingURIList;
-
   mozilla::WeakPtr<nsDocShell> mDocumentContainer;
 
   nsCString mCharacterSet;
diff --git a/dom/base/test/bug704320.sjs b/dom/base/test/bug704320.sjs
index dff77f4b3..e0f549533 100644
--- a/dom/base/test/bug704320.sjs
+++ b/dom/base/test/bug704320.sjs
@@ -194,12 +194,6 @@ function createPolicyTest(policy, optionalEarlierPolicy) {
 }
 
 function handleRequest(request, response) {
-  if (request.method == 'HEAD') {
-    // respond to a HEAD request with a 418 so that we can easily distinguish
-    // HSTS priming responses and ignore them
-    response.setStatusLine('1.1', 418, "I'm a teapot");
-    return;
-  }
   var sharedKey = 'bug704320.sjs';
   var params = request.queryString.split('&');
   var action = params[0].split('=')[1];
diff --git a/dom/base/test/referrerHelper.js b/dom/base/test/referrerHelper.js
index 207bf5f15..01a22829c 100644
--- a/dom/base/test/referrerHelper.js
+++ b/dom/base/test/referrerHelper.js
@@ -25,9 +25,6 @@ function doXHR(url, onSuccess, onFail) {
   xhr.onload = function () {
     if (xhr.status == 200) {
       onSuccess(xhr);
-    } else if (xhr.status == 418) {
-      // Ignore HSTS priming responses
-      return;
     } else {
       onFail(xhr);
     }
diff --git a/dom/html/test/test_anchor_ping.html b/dom/html/test/test_anchor_ping.html
index 4a39bcefe..6a1832ad1 100644
--- a/dom/html/test/test_anchor_ping.html
+++ b/dom/html/test/test_anchor_ping.html
@@ -40,15 +40,10 @@ let tests = [
   function* setup() {
     Services.prefs.setBoolPref("browser.send_pings", true);
     Services.prefs.setIntPref("browser.send_pings.max_per_link", -1);
-    Services.prefs.setBoolPref("security.mixed_content.block_active_content", false);
-    // The server we create can't handle the priming HEAD requests
-    Services.prefs.setBoolPref("security.mixed_content.send_hsts_priming", false);
 
     SimpleTest.registerCleanupFunction(() => {
       Services.prefs.clearUserPref("browser.send_pings");
       Services.prefs.clearUserPref("browser.send_pings.max_per_link");
-      Services.prefs.clearUserPref("security.mixed_content.block_active_content");
-      Services.prefs.clearUserPref("security.mixed_content.send_hsts_priming");
     });
   },
 
@@ -151,7 +146,7 @@ let tests = [
 
     // The referrer will be loaded using a secure channel.
     navigate("https://example.com/chrome/dom/html/test/" +
-             "file_anchor_ping.html?" + "http://localhost:" +
+             "file_anchor_ping.html?" + "http://127.0.0.1:" +
              server.identity.primaryPort + ping);
 
     // Wait until the ping has been sent.
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 9eebf3c34..3488e26bd 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -3373,13 +3373,13 @@ ContentParent::RecvIsSecureURI(const uint32_t& type,
 }
 
 bool
-ContentParent::RecvAccumulateMixedContentHSTS(const URIParams& aURI, const bool& aActive, const bool& aHSTSPriming)
+ContentParent::RecvAccumulateMixedContentHSTS(const URIParams& aURI, const bool& aActive)
 {
   nsCOMPtr<nsIURI> ourURI = DeserializeURI(aURI);
   if (!ourURI) {
     return false;
   }
-  nsMixedContentBlocker::AccumulateMixedContentHSTS(ourURI, aActive, aHSTSPriming);
+  nsMixedContentBlocker::AccumulateMixedContentHSTS(ourURI, aActive);
   return true;
 }
 
diff --git a/dom/ipc/ContentParent.h b/dom/ipc/ContentParent.h
index f1719c059..abcea0b65 100644
--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -742,8 +742,7 @@ private:
                                const uint32_t& aFlags, bool* aIsSecureURI) override;
 
   virtual bool RecvAccumulateMixedContentHSTS(const URIParams& aURI,
-                                              const bool& aActive,
-                                              const bool& aHSTSPriming) override;
+                                              const bool& aActive) override;
 
   virtual bool DeallocPHalParent(PHalParent*) override;
 
diff --git a/dom/ipc/PContent.ipdl b/dom/ipc/PContent.ipdl
index df9eeb147..c01ad59c1 100644
--- a/dom/ipc/PContent.ipdl
+++ b/dom/ipc/PContent.ipdl
@@ -661,7 +661,7 @@ parent:
     sync IsSecureURI(uint32_t type, URIParams uri, uint32_t flags)
         returns (bool isSecureURI);
 
-    async AccumulateMixedContentHSTS(URIParams uri, bool active, bool hasHSTSPriming);
+    async AccumulateMixedContentHSTS(URIParams uri, bool active);
 
     sync GetLookAndFeelCache()
         returns (LookAndFeelInt[] lookAndFeelIntCache);
diff --git a/dom/performance/PerformanceResourceTiming.cpp b/dom/performance/PerformanceResourceTiming.cpp
index 2eaa4eb9a..9c5475041 100644
--- a/dom/performance/PerformanceResourceTiming.cpp
+++ b/dom/performance/PerformanceResourceTiming.cpp
@@ -6,6 +6,7 @@
 
 #include "PerformanceResourceTiming.h"
 #include "mozilla/dom/PerformanceResourceTimingBinding.h"
+#include "mozilla/Unused.h"
 
 using namespace mozilla::dom;
 
diff --git a/dom/security/nsContentSecurityManager.cpp b/dom/security/nsContentSecurityManager.cpp
index c6558fc93..f329aa723 100644
--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -8,8 +8,6 @@
 #include "nsContentUtils.h"
 #include "nsCORSListenerProxy.h"
 #include "nsIStreamListener.h"
-#include "nsIDocument.h"
-#include "nsMixedContentBlocker.h"
 #include "nsCDefaultURIFixup.h"
 #include "nsIURIFixup.h"
 
@@ -507,13 +505,6 @@ DoContentSecurityChecks(nsIChannel* aChannel, nsILoadInfo* aLoadInfo)
     return NS_ERROR_CONTENT_BLOCKED;
   }
 
-  if (nsMixedContentBlocker::sSendHSTSPriming) {
-    rv = nsMixedContentBlocker::MarkLoadInfoForPriming(uri,
-                                                       requestingContext,
-                                                       aLoadInfo);
-    return rv;
-  }
-
   return NS_OK;
 }
 
diff --git a/dom/security/nsMixedContentBlocker.cpp b/dom/security/nsMixedContentBlocker.cpp
index 4e80dce3f..7d50a43a3 100644
--- a/dom/security/nsMixedContentBlocker.cpp
+++ b/dom/security/nsMixedContentBlocker.cpp
@@ -54,13 +54,6 @@ bool nsMixedContentBlocker::sBlockMixedScript = false;
 // Is mixed display content blocking (images, audio, video, <a ping>) enabled?
 bool nsMixedContentBlocker::sBlockMixedDisplay = false;
 
-// Do we move HSTS before mixed-content
-bool nsMixedContentBlocker::sUseHSTS = false;
-// Do we send an HSTS priming request
-bool nsMixedContentBlocker::sSendHSTSPriming = false;
-// Default HSTS Priming failure timeout to 7 days, in seconds
-uint32_t nsMixedContentBlocker::sHSTSPrimingCacheTimeout = (60 * 24 * 7);
-
 // Fired at the document that attempted to load mixed content.  The UI could
 // handle this event, for example, by displaying an info bar that offers the
 // choice to reload the page with mixed content permitted.
@@ -202,18 +195,6 @@ nsMixedContentBlocker::nsMixedContentBlocker()
   // Cache the pref for mixed display blocking
   Preferences::AddBoolVarCache(&sBlockMixedDisplay,
                                "security.mixed_content.block_display_content");
-
-  // Cache the pref for HSTS
-  Preferences::AddBoolVarCache(&sUseHSTS,
-                               "security.mixed_content.use_hsts");
-
-  // Cache the pref for sending HSTS priming
-  Preferences::AddBoolVarCache(&sSendHSTSPriming,
-                               "security.mixed_content.send_hsts_priming");
-
-  // Cache the pref for HSTS priming failure cache time
-  Preferences::AddUintVarCache(&sHSTSPrimingCacheTimeout,
-                               "security.mixed_content.hsts_priming_cache_timeout");
 }
 
 nsMixedContentBlocker::~nsMixedContentBlocker()
@@ -343,22 +324,6 @@ nsMixedContentBlocker::AsyncOnChannelRedirect(nsIChannel* aOldChannel,
     return NS_BINDING_FAILED;
   }
 
-  if (nsMixedContentBlocker::sSendHSTSPriming) {
-    // The LoadInfo passed in is for the original channel, HSTS priming needs to
-    // be set on the new channel, if required. If the redirect changes
-    // http->https, or vice-versa, the need for priming may change.
-    nsCOMPtr<nsILoadInfo> newLoadInfo;
-    rv = aNewChannel->GetLoadInfo(getter_AddRefs(newLoadInfo));
-    NS_ENSURE_SUCCESS(rv, rv);
-    rv = nsMixedContentBlocker::MarkLoadInfoForPriming(newUri,
-                                                       requestingContext,
-                                                       newLoadInfo);
-    if (NS_FAILED(rv)) {
-      decision = REJECT_REQUEST;
-      newLoadInfo->ClearHSTSPriming();
-    }
-  }
-
   // If the channel is about to load mixed content, abort the channel
   if (!NS_CP_ACCEPTED(decision)) {
     autoCallback.DontCallback();
@@ -691,12 +656,6 @@ nsMixedContentBlocker::ShouldLoad(bool aHadInsecureImageRedirect,
     // the parent is https, and the protocol associated with innerContentLocation
     // doesn't map to the secure URI flags checked above.  Assert this for
     // sanity's sake
-#ifdef DEBUG
-    bool isHttpsScheme = false;
-    rv = innerContentLocation->SchemeIs("https", &isHttpsScheme);
-    NS_ENSURE_SUCCESS(rv, rv);
-    MOZ_ASSERT(!isHttpsScheme);
-#endif
     *aDecision = REJECT_REQUEST;
     return NS_OK;
   }
@@ -836,34 +795,6 @@ nsMixedContentBlocker::ShouldLoad(bool aHadInsecureImageRedirect,
   }
   nsresult stateRV = securityUI->GetState(&state);
 
-  bool doHSTSPriming = false;
-  if (isHttpScheme) {
-    bool hsts = false;
-    bool cached = false;
-    nsCOMPtr<nsISiteSecurityService> sss =
-      do_GetService(NS_SSSERVICE_CONTRACTID, &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-    rv = sss->IsSecureURI(nsISiteSecurityService::HEADER_HSTS, aContentLocation,
-        0, &cached, &hsts);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    if (hsts && sUseHSTS) {
-      // assume we will be upgraded later
-      *aDecision = ACCEPT;
-      return NS_OK;
-    }
-
-    // Send a priming request if the result is not already cached and priming
-    // requests are allowed
-    if (!cached && sSendHSTSPriming) {
-      // add this URI as a priming location
-      doHSTSPriming = true;
-      document->AddHSTSPrimingLocation(innerContentLocation,
-          HSTSPrimingState::eHSTS_PRIMING_ALLOW);
-      *aDecision = ACCEPT;
-    }
-  }
-
   // At this point we know that the request is mixed content, and the only
   // question is whether we block it.  Record telemetry at this point as to
   // whether HSTS would have fixed things by making the content location
@@ -879,14 +810,14 @@ nsMixedContentBlocker::ShouldLoad(bool aHadInsecureImageRedirect,
   bool active = (classification == eMixedScript);
   if (!aHadInsecureImageRedirect) {
     if (XRE_IsParentProcess()) {
-      AccumulateMixedContentHSTS(innerContentLocation, active, doHSTSPriming);
+      AccumulateMixedContentHSTS(innerContentLocation, active);
     } else {
       // Ask the parent process to do the same call
       mozilla::dom::ContentChild* cc = mozilla::dom::ContentChild::GetSingleton();
       if (cc) {
         mozilla::ipc::URIParams uri;
         SerializeURI(innerContentLocation, uri);
-        cc->SendAccumulateMixedContentHSTS(uri, active, doHSTSPriming);
+        cc->SendAccumulateMixedContentHSTS(uri, active);
       }
     }
   }
@@ -929,13 +860,7 @@ nsMixedContentBlocker::ShouldLoad(bool aHadInsecureImageRedirect,
         }
       }
     } else {
-      if (doHSTSPriming) {
-        document->AddHSTSPrimingLocation(innerContentLocation,
-            HSTSPrimingState::eHSTS_PRIMING_BLOCK);
-        *aDecision = nsIContentPolicy::ACCEPT;
-      } else {
-        *aDecision = nsIContentPolicy::REJECT_REQUEST;
-      }
+      *aDecision = nsIContentPolicy::REJECT_REQUEST;
       LogMixedContentMessage(classification, aContentLocation, rootDoc, eBlocked);
       if (!rootDoc->GetHasMixedDisplayContentBlocked() && NS_SUCCEEDED(stateRV)) {
         rootDoc->SetHasMixedDisplayContentBlocked(true);
@@ -981,13 +906,7 @@ nsMixedContentBlocker::ShouldLoad(bool aHadInsecureImageRedirect,
       }
     } else {
       //User has not overriden the pref by Disabling protection. Reject the request and update the security state.
-      if (doHSTSPriming) {
-        document->AddHSTSPrimingLocation(innerContentLocation,
-            HSTSPrimingState::eHSTS_PRIMING_BLOCK);
-        *aDecision = nsIContentPolicy::ACCEPT;
-      } else {
-        *aDecision = nsIContentPolicy::REJECT_REQUEST;
-      }
+      *aDecision = nsIContentPolicy::REJECT_REQUEST;
       LogMixedContentMessage(classification, aContentLocation, rootDoc, eBlocked);
       // See if the pref will change here. If it will, only then do we need to call OnSecurityChange() to update the UI.
       if (rootDoc->GetHasMixedActiveContentBlocked()) {
@@ -1052,24 +971,10 @@ enum MixedContentHSTSState {
   MCB_HSTS_ACTIVE_WITH_HSTS  = 3
 };
 
-// Similar to the existing mixed-content HSTS, except MCB_HSTS_*_NO_HSTS is
-// broken into two distinct states, indicating whether we plan to send a priming
-// request or not. If we decided not go send a priming request, it could be
-// because it is a type we do not support, or because we cached a previous
-// negative response.
-enum MixedContentHSTSPrimingState {
-  eMCB_HSTS_PASSIVE_WITH_HSTS  = 0,
-  eMCB_HSTS_ACTIVE_WITH_HSTS   = 1,
-  eMCB_HSTS_PASSIVE_NO_PRIMING = 2,
-  eMCB_HSTS_PASSIVE_DO_PRIMING = 3,
-  eMCB_HSTS_ACTIVE_NO_PRIMING  = 4,
-  eMCB_HSTS_ACTIVE_DO_PRIMING  = 5
-};
-
 // Record information on when HSTS would have made mixed content not mixed
 // content (regardless of whether it was actually blocked)
 void
-nsMixedContentBlocker::AccumulateMixedContentHSTS(nsIURI* aURI, bool aActive, bool aHasHSTSPriming)
+nsMixedContentBlocker::AccumulateMixedContentHSTS(nsIURI* aURI, bool aActive)
 {
   // This method must only be called in the parent, because
   // nsSiteSecurityService is only available in the parent
@@ -1089,108 +994,26 @@ nsMixedContentBlocker::AccumulateMixedContentHSTS(nsIURI* aURI, bool aActive, bo
     return;
   }
 
-  // states: would upgrade, would prime, hsts info cached
+  // states: would upgrade, hsts info cached
   // active, passive
   //
   if (!aActive) {
     if (!hsts) {
       Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS,
                             MCB_HSTS_PASSIVE_NO_HSTS);
-      if (aHasHSTSPriming) {
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                              eMCB_HSTS_PASSIVE_DO_PRIMING);
-      } else {
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                              eMCB_HSTS_PASSIVE_NO_PRIMING);
-      }
     }
     else {
       Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS,
                             MCB_HSTS_PASSIVE_WITH_HSTS);
-      Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                            eMCB_HSTS_PASSIVE_WITH_HSTS);
     }
   } else {
     if (!hsts) {
       Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS,
                             MCB_HSTS_ACTIVE_NO_HSTS);
-      if (aHasHSTSPriming) {
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                              eMCB_HSTS_ACTIVE_DO_PRIMING);
-      } else {
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                              eMCB_HSTS_ACTIVE_NO_PRIMING);
-      }
     }
     else {
       Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS,
                             MCB_HSTS_ACTIVE_WITH_HSTS);
-      Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING,
-                            eMCB_HSTS_ACTIVE_WITH_HSTS);
     }
   }
-}
-
-//static
-nsresult
-nsMixedContentBlocker::MarkLoadInfoForPriming(nsIURI* aURI,
-                                              nsISupports* aRequestingContext,
-                                              nsILoadInfo* aLoadInfo)
-{
-  nsresult rv;
-  bool sendPriming = false;
-  bool mixedContentWouldBlock = false;
-  rv = GetHSTSPrimingFromRequestingContext(aURI,
-                                           aRequestingContext,
-                                           &sendPriming,
-                                           &mixedContentWouldBlock);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (sendPriming) {
-    aLoadInfo->SetHSTSPriming(mixedContentWouldBlock);
-  }
-
-  return NS_OK;
-}
-
-//static
-nsresult
-nsMixedContentBlocker::GetHSTSPrimingFromRequestingContext(nsIURI* aURI,
-    nsISupports* aRequestingContext,
-    bool* aSendPrimingRequest,
-    bool* aMixedContentWouldBlock)
-{
-  *aSendPrimingRequest = false;
-  *aMixedContentWouldBlock = false;
-  // If we marked for priming, we used the innermost URI, so get that
-  nsCOMPtr<nsIURI> innerURI = NS_GetInnermostURI(aURI);
-  if (!innerURI) {
-    NS_ERROR("Can't get innerURI from aContentLocation");
-    return NS_ERROR_CONTENT_BLOCKED;
-  }
-
-  bool isHttp = false;
-  innerURI->SchemeIs("http", &isHttp);
-  if (!isHttp) {
-    // there is nothign to do
-    return NS_OK;
-  }
-
-  // If the DocShell was marked for HSTS priming, propagate that to the LoadInfo
-  nsCOMPtr<nsIDocShell> docShell = NS_CP_GetDocShellFromContext(aRequestingContext);
-  if (!docShell) {
-    return NS_OK;
-  }
-  nsCOMPtr<nsIDocument> document = docShell->GetDocument();
-  if (!document) {
-    return NS_OK;
-  }
-
-  HSTSPrimingState status = document->GetHSTSPrimingStateForLocation(innerURI);
-  if (status != HSTSPrimingState::eNO_HSTS_PRIMING) {
-    *aSendPrimingRequest = (status != HSTSPrimingState::eNO_HSTS_PRIMING);
-    *aMixedContentWouldBlock = (status == HSTSPrimingState::eHSTS_PRIMING_BLOCK);
-  }
-
-  return NS_OK;
-}
+}
\ No newline at end of file
diff --git a/dom/security/nsMixedContentBlocker.h b/dom/security/nsMixedContentBlocker.h
index 539c3ebbb..56ab9621f 100644
--- a/dom/security/nsMixedContentBlocker.h
+++ b/dom/security/nsMixedContentBlocker.h
@@ -62,44 +62,11 @@ public:
                              nsIPrincipal* aRequestPrincipal,
                              int16_t* aDecision);
   static void AccumulateMixedContentHSTS(nsIURI* aURI,
-                                         bool aActive,
-                                         bool aHasHSTSPriming);
-  /* If the document associated with aRequestingContext requires priming for
-   * aURI, propagate that to the LoadInfo so the HttpChannel will find out about
-   * it.
-   *
-   * @param aURI The URI associated with the load
-   * @param aRequestingContext the requesting context passed to ShouldLoad
-   * @param aLoadInfo the LoadInfo for the load
-   */
-  static nsresult MarkLoadInfoForPriming(nsIURI* aURI,
-                                         nsISupports* aRequestingContext,
-                                         nsILoadInfo* aLoadInfo);
-
-  /* Given a context, return whether HSTS was marked on the document associated
-   * with the load for the given URI. This is used by MarkLoadInfoForPriming and
-   * directly by the image loader to determine whether to allow a load to occur
-   * from the cache.
-   *
-   * @param aURI The URI associated with the load
-   * @param aRequestingContext the requesting context passed to ShouldLoad
-   * @param aSendPrimingRequest out true if priming is required on the channel
-   * @param aMixedContentWouldBlock out true if mixed content would block
-   */
-  static nsresult GetHSTSPrimingFromRequestingContext(nsIURI* aURI,
-                                                      nsISupports* aRequestingContext,
-                                                      bool* aSendPrimingRequest,
-                                                      bool* aMixedContentWouldBlock);
+                                         bool aActive);
 
 
   static bool sBlockMixedScript;
   static bool sBlockMixedDisplay;
-  // Do we move HSTS before mixed-content
-  static bool sUseHSTS;
-  // Do we send an HSTS priming request
-  static bool sSendHSTSPriming;
-  // Default HSTS Priming failure timeout in seconds
-  static uint32_t sHSTSPrimingCacheTimeout;
 };
 
 #endif /* nsMixedContentBlocker_h___ */
diff --git a/dom/security/test/csp/test_referrerdirective.html b/dom/security/test/csp/test_referrerdirective.html
index 770fcc40b..f590460a0 100644
--- a/dom/security/test/csp/test_referrerdirective.html
+++ b/dom/security/test/csp/test_referrerdirective.html
@@ -116,8 +116,6 @@ SimpleTest.waitForExplicitFinish();
 SpecialPowers.pushPrefEnv({
     'set': [['security.mixed_content.block_active_content',   false],
             ['security.mixed_content.block_display_content',  false],
-            ['security.mixed_content.send_hsts_priming',  false],
-            ['security.mixed_content.use_hsts',  false],
     ]
     },
     function() {
diff --git a/dom/security/test/hsts/browser.ini b/dom/security/test/hsts/browser.ini
deleted file mode 100644
index ae75031df..000000000
--- a/dom/security/test/hsts/browser.ini
+++ /dev/null
@@ -1,19 +0,0 @@
-[DEFAULT]
-skip-if = debug # bug 1311599, bug 1311239, etc
-support-files =
-  head.js
-  file_priming-top.html
-  file_testserver.sjs
-  file_1x1.png
-  file_priming.js
-  file_stylesheet.css
-
-[browser_hsts-priming_allow_active.js]
-[browser_hsts-priming_block_active.js]
-[browser_hsts-priming_hsts_after_mixed.js]
-[browser_hsts-priming_allow_display.js]
-[browser_hsts-priming_block_display.js]
-[browser_hsts-priming_block_active_css.js]
-[browser_hsts-priming_block_active_with_redir_same.js]
-[browser_hsts-priming_no-duplicates.js]
-[browser_hsts-priming_cache-timeout.js]
diff --git a/dom/security/test/hsts/browser_hsts-priming_allow_active.js b/dom/security/test/hsts/browser_hsts-priming_allow_active.js
deleted file mode 100644
index a932b31b3..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_allow_active.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when active
- *   content is allowed.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "allow_active";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_allow_display.js b/dom/security/test/hsts/browser_hsts-priming_allow_display.js
deleted file mode 100644
index 06546ca65..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_allow_display.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when display
- *   content is allowed.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "allow_display";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_block_active.js b/dom/security/test/hsts/browser_hsts-priming_block_active.js
deleted file mode 100644
index a5478b185..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_block_active.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when active
- *   content is blocked.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_active";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_block_active_css.js b/dom/security/test/hsts/browser_hsts-priming_block_active_css.js
deleted file mode 100644
index 340d11483..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_block_active_css.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when active
- *   content is blocked for css.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_active_css";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_block_active_with_redir_same.js b/dom/security/test/hsts/browser_hsts-priming_block_active_with_redir_same.js
deleted file mode 100644
index 130a3d5ec..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_block_active_with_redir_same.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when active
- *   content is blocked and redirect to the same host should still upgrade.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_active_with_redir_same";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_block_display.js b/dom/security/test/hsts/browser_hsts-priming_block_display.js
deleted file mode 100644
index 4eca62718..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_block_display.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when display
- *   content is blocked.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_display";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_cache-timeout.js b/dom/security/test/hsts/browser_hsts-priming_cache-timeout.js
deleted file mode 100644
index 5416a71d2..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_cache-timeout.js
+++ /dev/null
@@ -1,36 +0,0 @@
-/*
- * Description of the test:
- * Test that the network.hsts_priming.cache_timeout preferene causes the cache
- * to timeout
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Observer.add_observers(Services);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_display";
-
-  SetupPrefTestEnvironment(which, [["security.mixed_content.hsts_priming_cache_timeout", 1]]);
-
-  yield execute_test("no-ssl", test_settings[which].mimetype);
-
-  let pre_promise = performance.now();
-
-  while ((performance.now() - pre_promise) < 2000) {
-    yield new Promise(function (resolve) {
-      setTimeout(resolve, 2000);
-    });
-  }
-
-  // clear the fact that we saw a priming request
-  test_settings[which].priming = {};
-
-  yield execute_test("no-ssl", test_settings[which].mimetype);
-  is(test_settings[which].priming["no-ssl"], true,
-    "Correctly send a priming request after expiration.");
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_hsts_after_mixed.js b/dom/security/test/hsts/browser_hsts-priming_hsts_after_mixed.js
deleted file mode 100644
index 89ea6fbeb..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_hsts_after_mixed.js
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Description of the test:
- *   Check that HSTS priming occurs correctly with mixed content when the
- *   mixed-content blocks before HSTS.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Services.obs.addObserver(Observer, "console-api-log-event", false);
-  Services.obs.addObserver(Observer, "http-on-examine-response", false);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "hsts_after_mixed";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/browser_hsts-priming_no-duplicates.js b/dom/security/test/hsts/browser_hsts-priming_no-duplicates.js
deleted file mode 100644
index 3846fe4f0..000000000
--- a/dom/security/test/hsts/browser_hsts-priming_no-duplicates.js
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * Description of the test:
- *   Only one request should be sent per host, even if we run the test more
- *   than once.
- */
-'use strict';
-
-//jscs:disable
-add_task(function*() {
-  //jscs:enable
-  Observer.add_observers(Services);
-  registerCleanupFunction(do_cleanup);
-
-  let which = "block_display";
-
-  SetupPrefTestEnvironment(which);
-
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  test_settings[which].priming = {};
-
-  // run the tests twice to validate the cache is being used
-  for (let server of Object.keys(test_servers)) {
-    yield execute_test(server, test_settings[which].mimetype);
-  }
-
-  SpecialPowers.popPrefEnv();
-});
diff --git a/dom/security/test/hsts/file_1x1.png b/dom/security/test/hsts/file_1x1.png
deleted file mode 100644
index 1ba31ba1a..000000000
--- a/dom/security/test/hsts/file_1x1.png
+++ /dev/null
diff --git a/dom/security/test/hsts/file_priming-top.html b/dom/security/test/hsts/file_priming-top.html
deleted file mode 100644
index b1d1bfa40..000000000
--- a/dom/security/test/hsts/file_priming-top.html
+++ /dev/null
@@ -1,84 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <title>Bug 1246540</title>
-  <meta http-equiv='content-type' content="text/html;charset=utf-8" />
-</head>
-<body>
-  <p id="display"></p>
-  <div id="content" style="visibility: hidden">
-  </div>
-
-<script type="text/javascript">
-/*
- * Description of the test:
- * Attempt to load an insecure resource. If the resource responds to HSTS
- * priming with an STS header, the load should continue securely.
- * If it does not, the load should continue be blocked or continue insecurely.
- */
-
-function parse_query_string() {
-  var q = {};
-  document.location.search.substr(1).
-    split('&').forEach(function (item, idx, ar) {
-      let [k, v] = item.split('=');
-      q[k] = unescape(v);
-    });
-  return q;
-}
-
-var args = parse_query_string();
-
-var subresources = {
-  css: { mimetype: 'text/css', file: 'file_stylesheet.css' },
-  img: { mimetype: 'image/png', file: 'file_1x1.png' },
-  script: { mimetype: 'text/javascript', file: 'file_priming.js' },
-};
-
-function handler(ev) {
-  console.log("HSTS_PRIMING: Blocked "+args.id);
-}
-
-function loadCss(src) {
-  let head = document.getElementsByTagName("head")[0];
-  let link = document.createElement("link");
-  link.setAttribute("rel", "stylesheet");
-  link.setAttribute("type", subresources[args.type].mimetype);
-  link.setAttribute("href", src);
-  head.appendChild(link);
-}
-
-function loadResource(src) {
-  let content = document.getElementById("content");
-  let testElem = document.createElement(args.type);
-  testElem.setAttribute("id", args.id);
-  testElem.setAttribute("charset", "UTF-8");
-  testElem.onerror = handler;
-  content.appendChild(testElem);
-  testElem.src = src;
-}
-
-function loadTest() {
-  let subresource = subresources[args.type];
-
-  let src = "http://"
-    + args.host
-    + "/browser/dom/security/test/hsts/file_testserver.sjs"
-    + "?file=" +escape("browser/dom/security/test/hsts/" + subresource.file)
-    + "&primer=" + escape(args.id)
-    + "&mimetype=" + escape(subresource.mimetype)
-    ;
-  if (args.type == 'css') {
-    loadCss(src);
-    return;
-  }
-
-  loadResource(src);
-}
-
-// start running the tests
-loadTest();
-
-</script>
-</body>
-</html>
diff --git a/dom/security/test/hsts/file_priming.js b/dom/security/test/hsts/file_priming.js
deleted file mode 100644
index 023022da6..000000000
--- a/dom/security/test/hsts/file_priming.js
+++ /dev/null
@@ -1,4 +0,0 @@
-function completed() {
-  return;
-}
-completed();
diff --git a/dom/security/test/hsts/file_stylesheet.css b/dom/security/test/hsts/file_stylesheet.css
deleted file mode 100644
index e69de29bb..000000000
--- a/dom/security/test/hsts/file_stylesheet.css
+++ /dev/null
diff --git a/dom/security/test/hsts/file_testserver.sjs b/dom/security/test/hsts/file_testserver.sjs
deleted file mode 100644
index d5cd6b17a..000000000
--- a/dom/security/test/hsts/file_testserver.sjs
+++ /dev/null
@@ -1,66 +0,0 @@
-// SJS file for HSTS mochitests
-
-Components.utils.import("resource://gre/modules/NetUtil.jsm");
-Components.utils.importGlobalProperties(["URLSearchParams"]);
-
-function loadFromFile(path) {
-  // Load the HTML to return in the response from file.
-  // Since it's relative to the cwd of the test runner, we start there and
-  // append to get to the actual path of the file.
-  var testFile =
-    Components.classes["@mozilla.org/file/directory_service;1"].
-    getService(Components.interfaces.nsIProperties).
-    get("CurWorkD", Components.interfaces.nsILocalFile);
-  var dirs = path.split("/");
-  for (var i = 0; i < dirs.length; i++) {
-    testFile.append(dirs[i]);
-  }
-  var testFileStream =
-    Components.classes["@mozilla.org/network/file-input-stream;1"].
-    createInstance(Components.interfaces.nsIFileInputStream);
-  testFileStream.init(testFile, -1, 0, 0);
-  var test = NetUtil.readInputStreamToString(testFileStream, testFileStream.available());
-  return test;
-}
-
-function handleRequest(request, response)
-{
-  const query = new URLSearchParams(request.queryString);
-
-  redir = query.get('redir');
-  if (redir == 'same') {
-    query.delete("redir");
-    response.setStatus(302);
-    let newURI = request.uri;
-    newURI.queryString = query.serialize();
-    response.setHeader("Location", newURI.spec)
-  }
-
-  // avoid confusing cache behaviors
-  response.setHeader("Cache-Control", "no-cache", false);
-
-  // if we have a priming header, check for required behavior
-  // and set header appropriately
-  if (request.hasHeader('Upgrade-Insecure-Requests')) {
-    var expected = query.get('primer');
-    if (expected == 'prime-hsts') {
-      // set it for 5 minutes
-      response.setHeader("Strict-Transport-Security", "max-age="+(60*5), false);
-    } else if (expected == 'reject-upgrade') {
-      response.setHeader("Strict-Transport-Security", "max-age=0", false);
-    }
-    response.write('');
-    return;
-  }
-
-  var file = query.get('file');
-  if (file) {
-    var mimetype = unescape(query.get('mimetype'));
-    response.setHeader("Content-Type", mimetype, false);
-    response.write(loadFromFile(unescape(file)));
-    return;
-  }
-
-  response.setHeader("Content-Type", "application/json", false);
-  response.write('{}');
-}
diff --git a/dom/security/test/hsts/head.js b/dom/security/test/hsts/head.js
deleted file mode 100644
index 362b36444..000000000
--- a/dom/security/test/hsts/head.js
+++ /dev/null
@@ -1,308 +0,0 @@
-/*
- * Description of the tests:
- *   Check that HSTS priming occurs correctly with mixed content
- *
- *   This test uses three hostnames, each of which treats an HSTS priming
- *   request differently.
- *   * no-ssl never returns an ssl response
- *   * reject-upgrade returns an ssl response, but with no STS header
- *   * prime-hsts returns an ssl response with the appropriate STS header
- *
- *   For each server, test that it response appropriately when the we allow
- *   or block active or display content, as well as when we send an hsts priming
- *   request, but do not change the order of mixed-content and HSTS.
- *
- *   Test use http-on-examine-response, so must be run in browser context.
- */
-'use strict';
-
-var TOP_URI = "https://example.com/browser/dom/security/test/hsts/file_priming-top.html";
-
-var test_servers = {
-  // a test server that does not support TLS
-  'no-ssl': {
-    host: 'example.co.jp',
-    response: false,
-    id: 'no-ssl',
-  },
-  // a test server which does not support STS upgrade
-  'reject-upgrade': {
-    host: 'example.org',
-    response: true,
-    id: 'reject-upgrade',
-  },
-  // a test server when sends an STS header when priming
-  'prime-hsts': {
-    host: 'test1.example.com',
-    response: true,
-    id: 'prime-hsts'
-  },
-};
-
-var test_settings = {
-  // mixed active content is allowed, priming will upgrade
-  allow_active: {
-    block_active: false,
-    block_display: false,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'script',
-    result: {
-      'no-ssl': 'insecure',
-      'reject-upgrade': 'insecure',
-      'prime-hsts': 'secure',
-    },
-  },
-  // mixed active content is blocked, priming will upgrade
-  block_active: {
-    block_active: true,
-    block_display: false,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'script',
-    result: {
-      'no-ssl': 'blocked',
-      'reject-upgrade': 'blocked',
-      'prime-hsts': 'secure',
-    },
-  },
-  // keep the original order of mixed-content and HSTS, but send
-  // priming requests
-  hsts_after_mixed: {
-    block_active: true,
-    block_display: false,
-    use_hsts: false,
-    send_hsts_priming: true,
-    type: 'script',
-    result: {
-      'no-ssl': 'blocked',
-      'reject-upgrade': 'blocked',
-      'prime-hsts': 'blocked',
-    },
-  },
-  // mixed display content is allowed, priming will upgrade
-  allow_display: {
-    block_active: true,
-    block_display: false,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'img',
-    result: {
-      'no-ssl': 'insecure',
-      'reject-upgrade': 'insecure',
-      'prime-hsts': 'secure',
-    },
-  },
-  // mixed display content is blocked, priming will upgrade
-  block_display: {
-    block_active: true,
-    block_display: true,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'img',
-    result: {
-      'no-ssl': 'blocked',
-      'reject-upgrade': 'blocked',
-      'prime-hsts': 'secure',
-    },
-  },
-  // mixed active content is blocked, priming will upgrade (css)
-  block_active_css: {
-    block_active: true,
-    block_display: false,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'css',
-    result: {
-      'no-ssl': 'blocked',
-      'reject-upgrade': 'blocked',
-      'prime-hsts': 'secure',
-    },
-  },
-  // mixed active content is blocked, priming will upgrade
-  // redirect to the same host
-  block_active_with_redir_same: {
-    block_active: true,
-    block_display: false,
-    use_hsts: true,
-    send_hsts_priming: true,
-    type: 'script',
-    redir: 'same',
-    result: {
-      'no-ssl': 'blocked',
-      'reject-upgrade': 'blocked',
-      'prime-hsts': 'secure',
-    },
-  },
-}
-// track which test we are on
-var which_test = "";
-
-const Observer = {
-  observe: function (subject, topic, data) {
-    switch (topic) {
-      case 'console-api-log-event':
-        return Observer.console_api_log_event(subject, topic, data);
-      case 'http-on-examine-response':
-        return Observer.http_on_examine_response(subject, topic, data);
-      case 'http-on-modify-request':
-        return Observer.http_on_modify_request(subject, topic, data);
-    }
-    throw "Can't handle topic "+topic;
-  },
-  add_observers: function (services) {
-    services.obs.addObserver(Observer, "console-api-log-event", false);
-    services.obs.addObserver(Observer, "http-on-examine-response", false);
-    services.obs.addObserver(Observer, "http-on-modify-request", false);
-  },
-  // When a load is blocked which results in an error event within a page, the
-  // test logs to the console.
-  console_api_log_event: function (subject, topic, data) {
-    var message = subject.wrappedJSObject.arguments[0];
-    // when we are blocked, this will match the message we sent to the console,
-    // ignore everything else.
-    var re = RegExp(/^HSTS_PRIMING: Blocked ([-\w]+).*$/);
-    if (!re.test(message)) {
-      return;
-    }
-
-    let id = message.replace(re, '$1');
-    let curTest =test_servers[id];
-
-    if (!curTest) {
-      ok(false, "HSTS priming got a console message blocked, "+
-          "but doesn't match expectations "+id+" (msg="+message);
-      return;
-    }
-
-    is("blocked", test_settings[which_test].result[curTest.id], "HSTS priming "+
-        which_test+":"+curTest.id+" expected "+
-        test_settings[which_test].result[curTest.id]+", got blocked");
-    test_settings[which_test].finished[curTest.id] = "blocked";
-  },
-  get_current_test: function(uri) {
-    for (let item in test_servers) {
-      let re = RegExp('https?://'+test_servers[item].host);
-      if (re.test(uri)) {
-        return test_servers[item];
-      }
-    }
-    return null;
-  },
-  http_on_modify_request: function (subject, topic, data) {
-    let channel = subject.QueryInterface(Ci.nsIHttpChannel);
-    if (channel.requestMethod != 'HEAD') {
-      return;
-    }
-
-    let curTest = this.get_current_test(channel.URI.asciiSpec);
-
-    if (!curTest) {
-      return;
-    }
-
-    ok(!(curTest.id in test_settings[which_test].priming), "Already saw a priming request for " + curTest.id);
-    test_settings[which_test].priming[curTest.id] = true;
-  },
-  // When we see a response come back, peek at the response and test it is secure
-  // or insecure as needed. Addtionally, watch the response for priming requests.
-  http_on_examine_response: function (subject, topic, data) {
-    let channel = subject.QueryInterface(Ci.nsIHttpChannel);
-    let curTest = this.get_current_test(channel.URI.asciiSpec);
-
-    if (!curTest) {
-      return;
-    }
-
-    let result = (channel.URI.asciiSpec.startsWith('https:')) ? "secure" : "insecure";
-
-    // This is a priming request, go ahead and validate we were supposed to see
-    // a response from the server
-    if (channel.requestMethod == 'HEAD') {
-      is(true, curTest.response, "HSTS priming response found " + curTest.id);
-      return;
-    }
-
-    // This is the response to our query, make sure it matches
-    is(result, test_settings[which_test].result[curTest.id],
-        "HSTS priming result " + which_test + ":" + curTest.id);
-    test_settings[which_test].finished[curTest.id] = result;
-  },
-};
-
-// opens `uri' in a new tab and focuses it.
-// returns the newly opened tab
-function openTab(uri) {
-  let tab = gBrowser.addTab(uri);
-
-  // select tab and make sure its browser is focused
-  gBrowser.selectedTab = tab;
-  tab.ownerDocument.defaultView.focus();
-
-  return tab;
-}
-
-function clear_sts_data() {
-  for (let test in test_servers) {
-    SpecialPowers.cleanUpSTSData('http://'+test_servers[test].host);
-  }
-}
-
-function do_cleanup() {
-  clear_sts_data();
-
-  Services.obs.removeObserver(Observer, "console-api-log-event");
-  Services.obs.removeObserver(Observer, "http-on-examine-response");
-}
-
-function SetupPrefTestEnvironment(which, additional_prefs) {
-  which_test = which;
-  clear_sts_data();
-
-  var settings = test_settings[which];
-  // priming counts how many priming requests we saw
-  settings.priming = {};
-  // priming counts how many tests were finished
-  settings.finished= {};
-
-  var prefs = [["security.mixed_content.block_active_content",
-                settings.block_active],
-               ["security.mixed_content.block_display_content",
-                settings.block_display],
-               ["security.mixed_content.use_hsts",
-                settings.use_hsts],
-               ["security.mixed_content.send_hsts_priming",
-                settings.send_hsts_priming]];
-
-  if (additional_prefs) {
-    for (let idx in additional_prefs) {
-      prefs.push(additional_prefs[idx]);
-    }
-  }
-
-  console.log("prefs=%s", prefs);
-
-  SpecialPowers.pushPrefEnv({'set': prefs});
-}
-
-// make the top-level test uri
-function build_test_uri(base_uri, host, test_id, type) {
-  return base_uri +
-          "?host=" + escape(host) +
-          "&id=" + escape(test_id) +
-          "&type=" + escape(type);
-}
-
-// open a new tab, load the test, and wait for it to finish
-function execute_test(test, mimetype) {
-  var src = build_test_uri(TOP_URI, test_servers[test].host,
-      test, test_settings[which_test].type);
-
-  let tab = openTab(src);
-  test_servers[test]['tab'] = tab;
-
-  let browser = gBrowser.getBrowserForTab(tab);
-  yield BrowserTestUtils.browserLoaded(browser);
-
-  yield BrowserTestUtils.removeTab(tab);
-}
diff --git a/dom/security/test/mixedcontentblocker/test_main.html b/dom/security/test/mixedcontentblocker/test_main.html
index d2bc9dc7e..bb9536939 100644
--- a/dom/security/test/mixedcontentblocker/test_main.html
+++ b/dom/security/test/mixedcontentblocker/test_main.html
@@ -162,9 +162,6 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=62178
   }
 
   function startTest() {
-    // Set prefs to use mixed-content before HSTS
-    SpecialPowers.pushPrefEnv({'set': [["security.mixed_content.use_hsts", false],
-                                       ["security.mixed_content.send_hsts_priming", false]]});
     //Set the first set of mixed content settings and increment the counter.
     changePrefs([], function() {
       //listen for a messages from the mixed content test harness
diff --git a/dom/security/test/moz.build b/dom/security/test/moz.build
index 946959dee..759e76c73 100644
--- a/dom/security/test/moz.build
+++ b/dom/security/test/moz.build
@@ -28,5 +28,4 @@ BROWSER_CHROME_MANIFESTS += [
     'contentverifier/browser.ini',
     'csp/browser.ini',
     'general/browser.ini',
-    'hsts/browser.ini',
 ]
diff --git a/image/imgLoader.cpp b/image/imgLoader.cpp
index 5e5ee7829..f7fb657bd 100644
--- a/image/imgLoader.cpp
+++ b/image/imgLoader.cpp
@@ -607,19 +607,6 @@ ShouldLoadCachedImage(imgRequest* aImgRequest,
     }
   }
 
-  bool sendPriming = false;
-  bool mixedContentWouldBlock = false;
-  rv = nsMixedContentBlocker::GetHSTSPrimingFromRequestingContext(contentLocation,
-      aLoadingContext, &sendPriming, &mixedContentWouldBlock);
-  if (NS_FAILED(rv)) {
-    return false;
-  }
-  if (sendPriming && mixedContentWouldBlock) {
-    // if either of the securty checks above would cause a priming request, we
-    // can't load this image from the cache, so go ahead and return false here
-    return false;
-  }
-
   return true;
 }
 
diff --git a/ipc/glue/BackgroundUtils.cpp b/ipc/glue/BackgroundUtils.cpp
index e115fa74c..44f988efd 100644
--- a/ipc/glue/BackgroundUtils.cpp
+++ b/ipc/glue/BackgroundUtils.cpp
@@ -295,9 +295,8 @@ LoadInfoToLoadInfoArgs(nsILoadInfo *aLoadInfo,
       aLoadInfo->CorsUnsafeHeaders(),
       aLoadInfo->GetForcePreflight(),
       aLoadInfo->GetIsPreflight(),
-      aLoadInfo->GetLoadTriggeredFromExternal(),
-      aLoadInfo->GetForceHSTSPriming(),
-      aLoadInfo->GetMixedContentWouldBlock());
+      aLoadInfo->GetLoadTriggeredFromExternal()
+      );
 
   return NS_OK;
 }
@@ -373,9 +372,7 @@ LoadInfoArgsToLoadInfo(const OptionalLoadInfoArgs& aOptionalLoadInfoArgs,
                           loadInfoArgs.corsUnsafeHeaders(),
                           loadInfoArgs.forcePreflight(),
                           loadInfoArgs.isPreflight(),
-                          loadInfoArgs.loadTriggeredFromExternal(),
-                          loadInfoArgs.forceHSTSPriming(),
-                          loadInfoArgs.mixedContentWouldBlock()
+                          loadInfoArgs.loadTriggeredFromExternal()
                           );
 
    loadInfo.forget(outLoadInfo);
diff --git a/js/ipc/JavaScriptParent.cpp b/js/ipc/JavaScriptParent.cpp
index 7fe92d662..ca0a0bd21 100644
--- a/js/ipc/JavaScriptParent.cpp
+++ b/js/ipc/JavaScriptParent.cpp
@@ -16,6 +16,7 @@
 #include "xpcprivate.h"
 #include "mozilla/Casting.h"
 #include "mozilla/Telemetry.h"
+#include "mozilla/Unused.h"
 #include "nsAutoPtr.h"
 
 using namespace js;
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 18e23ff2e..1706807e9 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5447,23 +5447,6 @@ pref("media.block-autoplay-until-in-foreground", false);
 pref("layout.css.servo.enabled", true);
 #endif
 
-// HSTS Priming
-// If a request is mixed-content, send an HSTS priming request to attempt to
-// see if it is available over HTTPS.
-#ifdef RELEASE_OR_BETA
-// Don't change the order of evaluation of mixed-content and HSTS upgrades in
-// order to be most compatible with current standards
-pref("security.mixed_content.send_hsts_priming", false);
-pref("security.mixed_content.use_hsts", false);
-#else
-// Change the order of evaluation so HSTS upgrades happen before
-// mixed-content blocking
-pref("security.mixed_content.send_hsts_priming", true);
-pref("security.mixed_content.use_hsts", true);
-#endif
-// Approximately 1 week default cache for HSTS priming failures
-pref ("security.mixed_content.hsts_priming_cache_timeout", 10080);
-
 // TODO: Bug 1380959: Block toplevel data: URI navigations
 // If true, all toplevel data: URI navigations will be blocked.
 // Please note that manually entering a data: URI in the
diff --git a/netwerk/base/LoadInfo.cpp b/netwerk/base/LoadInfo.cpp
index ede825b8f..a8c9a5a25 100644
--- a/netwerk/base/LoadInfo.cpp
+++ b/netwerk/base/LoadInfo.cpp
@@ -67,8 +67,6 @@ LoadInfo::LoadInfo(nsIPrincipal* aLoadingPrincipal,
   , mForcePreflight(false)
   , mIsPreflight(false)
   , mLoadTriggeredFromExternal(false)
-  , mForceHSTSPriming(false)
-  , mMixedContentWouldBlock(false)
 {
   MOZ_ASSERT(mLoadingPrincipal);
   MOZ_ASSERT(mTriggeringPrincipal);
@@ -243,8 +241,6 @@ LoadInfo::LoadInfo(nsPIDOMWindowOuter* aOuterWindow,
   , mForcePreflight(false)
   , mIsPreflight(false)
   , mLoadTriggeredFromExternal(false)
-  , mForceHSTSPriming(false)
-  , mMixedContentWouldBlock(false)
 {
   // Top-level loads are never third-party
   // Grab the information we can out of the window.
@@ -308,8 +304,6 @@ LoadInfo::LoadInfo(const LoadInfo& rhs)
   , mForcePreflight(rhs.mForcePreflight)
   , mIsPreflight(rhs.mIsPreflight)
   , mLoadTriggeredFromExternal(rhs.mLoadTriggeredFromExternal)
-  , mForceHSTSPriming(rhs.mForceHSTSPriming)
-  , mMixedContentWouldBlock(rhs.mMixedContentWouldBlock)
 {
 }
 
@@ -337,9 +331,7 @@ LoadInfo::LoadInfo(nsIPrincipal* aLoadingPrincipal,
                    const nsTArray<nsCString>& aCorsUnsafeHeaders,
                    bool aForcePreflight,
                    bool aIsPreflight,
-                   bool aLoadTriggeredFromExternal,
-                   bool aForceHSTSPriming,
-                   bool aMixedContentWouldBlock)
+                   bool aLoadTriggeredFromExternal)
   : mLoadingPrincipal(aLoadingPrincipal)
   , mTriggeringPrincipal(aTriggeringPrincipal)
   , mPrincipalToInherit(aPrincipalToInherit)
@@ -363,8 +355,6 @@ LoadInfo::LoadInfo(nsIPrincipal* aLoadingPrincipal,
   , mForcePreflight(aForcePreflight)
   , mIsPreflight(aIsPreflight)
   , mLoadTriggeredFromExternal(aLoadTriggeredFromExternal)
-  , mForceHSTSPriming (aForceHSTSPriming)
-  , mMixedContentWouldBlock(aMixedContentWouldBlock)
 {
   // Only top level TYPE_DOCUMENT loads can have a null loadingPrincipal
   MOZ_ASSERT(mLoadingPrincipal || aContentPolicyType == nsIContentPolicy::TYPE_DOCUMENT);
@@ -933,34 +923,6 @@ LoadInfo::GetLoadTriggeredFromExternal(bool* aLoadTriggeredFromExternal)
 }
 
 NS_IMETHODIMP
-LoadInfo::GetForceHSTSPriming(bool* aForceHSTSPriming)
-{
-  *aForceHSTSPriming = mForceHSTSPriming;
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-LoadInfo::GetMixedContentWouldBlock(bool *aMixedContentWouldBlock)
-{
-  *aMixedContentWouldBlock = mMixedContentWouldBlock;
-  return NS_OK;
-}
-
-void
-LoadInfo::SetHSTSPriming(bool aMixedContentWouldBlock)
-{
-  mForceHSTSPriming = true;
-  mMixedContentWouldBlock = aMixedContentWouldBlock;
-}
-
-void
-LoadInfo::ClearHSTSPriming()
-{
-  mForceHSTSPriming = false;
-  mMixedContentWouldBlock = false;
-}
-
-NS_IMETHODIMP
 LoadInfo::GetTainting(uint32_t* aTaintingOut)
 {
   MOZ_ASSERT(aTaintingOut);
diff --git a/netwerk/base/LoadInfo.h b/netwerk/base/LoadInfo.h
index 0ae6061b3..2b1e8c9e8 100644
--- a/netwerk/base/LoadInfo.h
+++ b/netwerk/base/LoadInfo.h
@@ -111,9 +111,7 @@ private:
            const nsTArray<nsCString>& aUnsafeHeaders,
            bool aForcePreflight,
            bool aIsPreflight,
-           bool aLoadTriggeredFromExternal,
-           bool aForceHSTSPriming,
-           bool aMixedContentWouldBlock);
+           bool aLoadTriggeredFromExternal);
   LoadInfo(const LoadInfo& rhs);
 
   friend nsresult
@@ -159,9 +157,6 @@ private:
   bool                             mForcePreflight;
   bool                             mIsPreflight;
   bool                             mLoadTriggeredFromExternal;
-
-  bool                             mForceHSTSPriming : 1;
-  bool                             mMixedContentWouldBlock : 1;
 };
 
 } // namespace net
diff --git a/netwerk/base/nsILoadInfo.idl b/netwerk/base/nsILoadInfo.idl
index 4ec29b972..9a883ff98 100644
--- a/netwerk/base/nsILoadInfo.idl
+++ b/netwerk/base/nsILoadInfo.idl
@@ -671,32 +671,6 @@ interface nsILoadInfo : nsISupports
   [infallible] readonly attribute boolean isPreflight;
 
   /**
-   * When this request would be mixed-content and we do not have an
-   * entry in the HSTS cache, we send an HSTS priming request to
-   * determine if it is ok to upgrade the request to HTTPS.
-   */
-  /**
-   * True if this is a mixed-content load and HSTS priming request will be sent.
-   */
-  [noscript, infallible] readonly attribute boolean forceHSTSPriming;
-  /**
-   * Carry the decision whether this load would be blocked by mixed content so
-   * that if HSTS priming fails, the correct decision can be made.
-   */
-  [noscript, infallible] readonly attribute boolean mixedContentWouldBlock;
-
-  /**
-   * Mark this LoadInfo as needing HSTS Priming
-   *
-   * @param wouldBlock Carry the decision of Mixed Content Blocking to be
-   * applied when HSTS priming is complete.
-   */
-  [noscript, notxpcom, nostdcall]
-  void setHSTSPriming(in boolean mixeContentWouldBlock);
-  [noscript, notxpcom, nostdcall]
-  void clearHSTSPriming();
-
-  /**
   * Constants reflecting the channel tainting.  These are mainly defined here
   * for script.  Internal C++ code should use the enum defined in LoadTainting.h.
   * See LoadTainting.h for documentation.
diff --git a/netwerk/ipc/NeckoChannelParams.ipdlh b/netwerk/ipc/NeckoChannelParams.ipdlh
index bb7562c64..2633ef608 100644
--- a/netwerk/ipc/NeckoChannelParams.ipdlh
+++ b/netwerk/ipc/NeckoChannelParams.ipdlh
@@ -56,8 +56,6 @@ struct LoadInfoArgs
   bool                  forcePreflight;
   bool                  isPreflight;
   bool                  loadTriggeredFromExternal;
-  bool                  forceHSTSPriming;
-  bool                  mixedContentWouldBlock;
 };
 
 /**
diff --git a/netwerk/protocol/http/HSTSPrimerListener.cpp b/netwerk/protocol/http/HSTSPrimerListener.cpp
deleted file mode 100644
index 8c9d28d36..000000000
--- a/netwerk/protocol/http/HSTSPrimerListener.cpp
+++ /dev/null
@@ -1,273 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsHttp.h"
-
-#include "HSTSPrimerListener.h"
-#include "nsIHstsPrimingCallback.h"
-#include "nsIPrincipal.h"
-#include "nsSecurityHeaderParser.h"
-#include "nsISiteSecurityService.h"
-#include "nsISocketProvider.h"
-#include "nsISSLStatus.h"
-#include "nsISSLStatusProvider.h"
-#include "nsStreamUtils.h"
-#include "nsHttpChannel.h"
-#include "LoadInfo.h"
-
-namespace mozilla {
-namespace net {
-
-using namespace mozilla;
-
-NS_IMPL_ISUPPORTS(HSTSPrimingListener, nsIStreamListener,
-                  nsIRequestObserver, nsIInterfaceRequestor)
-
-NS_IMETHODIMP
-HSTSPrimingListener::GetInterface(const nsIID & aIID, void **aResult)
-{
-  return QueryInterface(aIID, aResult);
-}
-
-NS_IMETHODIMP
-HSTSPrimingListener::OnStartRequest(nsIRequest *aRequest,
-                                    nsISupports *aContext)
-{
-  nsresult primingResult = CheckHSTSPrimingRequestStatus(aRequest);
-  nsCOMPtr<nsIHstsPrimingCallback> callback(mCallback);
-  mCallback = nullptr;
-
-  nsCOMPtr<nsITimedChannel> timingChannel =
-    do_QueryInterface(callback);
-  if (timingChannel) {
-    TimeStamp channelCreationTime;
-    nsresult rv = timingChannel->GetChannelCreation(&channelCreationTime);
-    if (NS_SUCCEEDED(rv) && !channelCreationTime.IsNull()) {
-      PRUint32 interval =
-        (PRUint32) (TimeStamp::Now() - channelCreationTime).ToMilliseconds();
-      Telemetry::Accumulate(Telemetry::HSTS_PRIMING_REQUEST_DURATION,
-          (NS_SUCCEEDED(primingResult)) ? NS_LITERAL_CSTRING("success")
-                                        : NS_LITERAL_CSTRING("failure"),
-          interval);
-    }
-  }
-
-  if (NS_FAILED(primingResult)) {
-    LOG(("HSTS Priming Failed (request was not approved)"));
-    return callback->OnHSTSPrimingFailed(primingResult, false);
-  }
-
-  LOG(("HSTS Priming Succeeded (request was approved)"));
-  return callback->OnHSTSPrimingSucceeded(false);
-}
-
-NS_IMETHODIMP
-HSTSPrimingListener::OnStopRequest(nsIRequest *aRequest,
-                                   nsISupports *aContext,
-                                   nsresult aStatus)
-{
-  return NS_OK;
-}
-
-nsresult
-HSTSPrimingListener::CheckHSTSPrimingRequestStatus(nsIRequest* aRequest)
-{
-  nsresult status;
-  nsresult rv = aRequest->GetStatus(&status);
-  NS_ENSURE_SUCCESS(rv, rv);
-  if (NS_FAILED(status)) {
-    return NS_ERROR_CONTENT_BLOCKED;
-  }
-
-  // Test that things worked on a HTTP level
-  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aRequest);
-  NS_ENSURE_STATE(httpChannel);
-  nsCOMPtr<nsIHttpChannelInternal> internal = do_QueryInterface(aRequest);
-  NS_ENSURE_STATE(internal);
-
-  bool succeedded;
-  rv = httpChannel->GetRequestSucceeded(&succeedded);
-  if (NS_FAILED(rv) || !succeedded) {
-    // If the request did not return a 2XX response, don't process it
-    return NS_ERROR_CONTENT_BLOCKED;
-  }
-
-  bool synthesized = false;
-  nsHttpChannel* rawHttpChannel = static_cast<nsHttpChannel*>(httpChannel.get());
-  rv = rawHttpChannel->GetResponseSynthesized(&synthesized);
-  NS_ENSURE_SUCCESS(rv, rv);
-  if (synthesized) {
-    // Don't consider synthesized responses
-    return NS_ERROR_CONTENT_BLOCKED;
-  }
-
-  // check to see if the HSTS cache was updated
-  nsCOMPtr<nsISiteSecurityService> sss = do_GetService(NS_SSSERVICE_CONTRACTID, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsCOMPtr<nsIURI> uri;
-  rv = httpChannel->GetURI(getter_AddRefs(uri));
-  NS_ENSURE_SUCCESS(rv, rv);
-  NS_ENSURE_TRUE(uri, NS_ERROR_CONTENT_BLOCKED);
-
-  bool hsts;
-  rv = sss->IsSecureURI(nsISiteSecurityService::HEADER_HSTS, uri, 0, nullptr, &hsts);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (hsts) {
-    // An HSTS upgrade was found
-    return NS_OK;
-  }
-
-  // There is no HSTS upgrade available
-  return NS_ERROR_CONTENT_BLOCKED;
-}
-
-/** nsIStreamListener methods **/
-
-NS_IMETHODIMP
-HSTSPrimingListener::OnDataAvailable(nsIRequest *aRequest,
-                                     nsISupports *ctxt,
-                                     nsIInputStream *inStr,
-                                     uint64_t sourceOffset,
-                                     uint32_t count)
-{
-  uint32_t totalRead;
-  return inStr->ReadSegments(NS_DiscardSegment, nullptr, count, &totalRead);
-}
-
-// static
-nsresult
-HSTSPrimingListener::StartHSTSPriming(nsIChannel* aRequestChannel,
-                                      nsIHstsPrimingCallback* aCallback)
-{
-
-  nsCOMPtr<nsIURI> finalChannelURI;
-  nsresult rv = NS_GetFinalChannelURI(aRequestChannel, getter_AddRefs(finalChannelURI));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsCOMPtr<nsIURI> uri;
-  rv = NS_GetSecureUpgradedURI(finalChannelURI, getter_AddRefs(uri));
-  NS_ENSURE_SUCCESS(rv,rv);
-
-  // check the HSTS cache
-  bool hsts;
-  bool cached;
-  nsCOMPtr<nsISiteSecurityService> sss = do_GetService(NS_SSSERVICE_CONTRACTID, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
-  rv = sss->IsSecureURI(nsISiteSecurityService::HEADER_HSTS, uri, 0, &cached, &hsts);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (hsts) {
-    // already saw this host and will upgrade if allowed by preferences
-    return aCallback->OnHSTSPrimingSucceeded(true);
-  }
-
-  if (cached) {
-    // there is a non-expired entry in the cache that doesn't allow us to
-    // upgrade, so go ahead and fail early.
-    return aCallback->OnHSTSPrimingFailed(NS_ERROR_CONTENT_BLOCKED, true);
-  }
-
-  // Either it wasn't cached or the cached result has expired. Build a
-  // channel for the HEAD request.
-
-  nsCOMPtr<nsILoadInfo> originalLoadInfo = aRequestChannel->GetLoadInfo();
-  MOZ_ASSERT(originalLoadInfo, "can not perform HSTS priming without a loadInfo");
-  if (!originalLoadInfo) {
-    return NS_ERROR_FAILURE;
-  }
-
-  nsCOMPtr<nsILoadInfo> loadInfo = static_cast<mozilla::LoadInfo*>
-    (originalLoadInfo.get())->CloneForNewRequest();
-
-  // the LoadInfo must have a security flag set in order to pass through priming
-  // if none of these security flags are set, go ahead and fail now instead of
-  // crashing in nsContentSecurityManager::ValidateSecurityFlags
-  nsSecurityFlags securityMode = loadInfo->GetSecurityMode();
-  if (securityMode != nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_DATA_INHERITS &&
-      securityMode != nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_DATA_IS_BLOCKED &&
-      securityMode != nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_INHERITS &&
-      securityMode != nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_IS_NULL &&
-      securityMode != nsILoadInfo::SEC_REQUIRE_CORS_DATA_INHERITS) {
-    return aCallback->OnHSTSPrimingFailed(NS_ERROR_CONTENT_BLOCKED, true);
-  }
-
-  nsCOMPtr<nsILoadGroup> loadGroup;
-  rv = aRequestChannel->GetLoadGroup(getter_AddRefs(loadGroup));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsLoadFlags loadFlags;
-  rv = aRequestChannel->GetLoadFlags(&loadFlags);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  loadFlags &= HttpBaseChannel::INHIBIT_CACHING |
-               HttpBaseChannel::INHIBIT_PERSISTENT_CACHING |
-               HttpBaseChannel::LOAD_BYPASS_CACHE |
-               HttpBaseChannel::LOAD_FROM_CACHE |
-               HttpBaseChannel::VALIDATE_ALWAYS;
-  // Priming requests should never be intercepted by service workers and
-  // are always anonymous.
-  loadFlags |= nsIChannel::LOAD_BYPASS_SERVICE_WORKER |
-               nsIRequest::LOAD_ANONYMOUS;
-
-  // Create a new channel to send the priming request
-  nsCOMPtr<nsIChannel> primingChannel;
-  rv = NS_NewChannelInternal(getter_AddRefs(primingChannel),
-                             uri,
-                             loadInfo,
-                             loadGroup,
-                             nullptr,   // aCallbacks are set later
-                             loadFlags);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  // Set method and headers
-  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(primingChannel);
-  if (!httpChannel) {
-    NS_ERROR("HSTSPrimingListener: Failed to QI to nsIHttpChannel!");
-    return NS_ERROR_FAILURE;
-  }
-
-  // Currently using HEAD per the draft, but under discussion to change to GET
-  // with credentials so if the upgrade is approved the result is already cached.
-  rv = httpChannel->SetRequestMethod(NS_LITERAL_CSTRING("HEAD"));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  rv = httpChannel->
-    SetRequestHeader(NS_LITERAL_CSTRING("Upgrade-Insecure-Requests"),
-                     NS_LITERAL_CSTRING("1"), false);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  // attempt to set the class of service flags on the new channel
-  nsCOMPtr<nsIClassOfService> requestClass = do_QueryInterface(aRequestChannel);
-  if (!requestClass) {
-    NS_ERROR("HSTSPrimingListener: aRequestChannel is not an nsIClassOfService");
-    return NS_ERROR_FAILURE;
-  }
-  nsCOMPtr<nsIClassOfService> primingClass = do_QueryInterface(httpChannel);
-  if (!primingClass) {
-    NS_ERROR("HSTSPrimingListener: aRequestChannel is not an nsIClassOfService");
-    return NS_ERROR_FAILURE;
-  }
-
-  uint32_t classFlags = 0;
-  rv = requestClass ->GetClassFlags(&classFlags);
-  NS_ENSURE_SUCCESS(rv, rv);
-  rv = primingClass->SetClassFlags(classFlags);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  // Set up listener which will start the original channel
-  nsCOMPtr<nsIStreamListener> primingListener(new HSTSPrimingListener(aCallback));
-
-  // Start priming
-  rv = primingChannel->AsyncOpen2(primingListener);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  return NS_OK;
-}
-
-} // namespace net
-} // namespace mozilla
diff --git a/netwerk/protocol/http/HSTSPrimerListener.h b/netwerk/protocol/http/HSTSPrimerListener.h
deleted file mode 100644
index 05089911b..000000000
--- a/netwerk/protocol/http/HSTSPrimerListener.h
+++ /dev/null
@@ -1,108 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef HSTSPrimingListener_h__
-#define HSTSPrimingListener_h__
-
-#include "nsCOMPtr.h"
-#include "nsIChannelEventSink.h"
-#include "nsIInterfaceRequestor.h"
-#include "nsIStreamListener.h"
-#include "nsIThreadRetargetableStreamListener.h"
-
-#include "mozilla/Attributes.h"
-
-class nsIPrincipal;
-class nsINetworkInterceptController;
-class nsIHstsPrimingCallback;
-
-namespace mozilla {
-namespace net {
-
-class HttpChannelParent;
-class nsHttpChannel;
-
-/*
- * How often do we get back an HSTS priming result which upgrades the connection to HTTPS?
- */
-enum HSTSPrimingResult {
-  // This site has been seen before and won't be upgraded
-  eHSTS_PRIMING_CACHED_NO_UPGRADE = 0,
-  // This site has been seen before and will be upgraded
-  eHSTS_PRIMING_CACHED_DO_UPGRADE = 1,
-  // This site has been seen before and will be blocked
-  eHSTS_PRIMING_CACHED_BLOCK      = 2,
-  // The request was already upgraded, probably through
-  // upgrade-insecure-requests
-  eHSTS_PRIMING_ALREADY_UPGRADED  = 3,
-  // HSTS priming is successful and the connection will be upgraded to HTTPS
-  eHSTS_PRIMING_SUCCEEDED         = 4,
-  // When priming succeeds, but preferences require preservation of the order
-  // of mixed-content and hsts, and mixed-content blocks the load
-  eHSTS_PRIMING_SUCCEEDED_BLOCK   = 5,
-  // When priming succeeds, but preferences require preservation of the order
-  // of mixed-content and hsts, and mixed-content allows the load over http
-  eHSTS_PRIMING_SUCCEEDED_HTTP    = 6,
-  // HSTS priming failed, and the load is blocked by mixed-content
-  eHSTS_PRIMING_FAILED_BLOCK      = 7,
-  // HSTS priming failed, and the load is allowed by mixed-content
-  eHSTS_PRIMING_FAILED_ACCEPT     = 8
-};
-
-//////////////////////////////////////////////////////////////////////////
-// Class used as streamlistener and notification callback when
-// doing the HEAD request for an HSTS Priming check. Needs to be an
-// nsIStreamListener in order to receive events from AsyncOpen2
-class HSTSPrimingListener final : public nsIStreamListener,
-                                  public nsIInterfaceRequestor
-{
-public:
-  explicit HSTSPrimingListener(nsIHstsPrimingCallback* aCallback)
-   : mCallback(aCallback)
-  {
-  }
-
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSISTREAMLISTENER
-  NS_DECL_NSIREQUESTOBSERVER
-  NS_DECL_NSIINTERFACEREQUESTOR
-
-private:
-  ~HSTSPrimingListener() {}
-
-  // Only nsHttpChannel can invoke HSTS priming
-  friend class mozilla::net::nsHttpChannel;
-
-  /**
-   * Start the HSTS priming request. This will send an anonymous HEAD request to
-   * the URI aRequestChannel is attempting to load. On success, the new HSTS
-   * priming channel is allocated in aHSTSPrimingChannel.
-   *
-   * @param aRequestChannel the reference channel used to initialze the HSTS
-   *        priming channel
-   * @param aCallback the callback stored to handle the results of HSTS priming.
-   * @param aHSTSPrimingChannel if the new HSTS priming channel is allocated
-   *        successfully, it will be placed here.
-   */
-  static nsresult StartHSTSPriming(nsIChannel* aRequestChannel,
-                                   nsIHstsPrimingCallback* aCallback);
-
-  /**
-   * Given a request, return NS_OK if it has resulted in a cached HSTS update.
-   * We don't need to check for the header as that has already been done for us.
-   */
-  nsresult CheckHSTSPrimingRequestStatus(nsIRequest* aRequest);
-
-  /**
-   * the nsIHttpChannel to notify with the result of HSTS priming.
-   */
-  nsCOMPtr<nsIHstsPrimingCallback> mCallback;
-};
-
-
-}} // mozilla::net
-
-#endif // HSTSPrimingListener_h__
diff --git a/netwerk/protocol/http/HttpChannelChild.cpp b/netwerk/protocol/http/HttpChannelChild.cpp
index 6d09135c4..0a1e0f859 100644
--- a/netwerk/protocol/http/HttpChannelChild.cpp
+++ b/netwerk/protocol/http/HttpChannelChild.cpp
@@ -1681,8 +1681,8 @@ NS_IMETHODIMP
 HttpChannelChild::OnRedirectVerifyCallback(nsresult result)
 {
   LOG(("HttpChannelChild::OnRedirectVerifyCallback [this=%p]\n", this));
-  nsresult rv;
   OptionalURIParams redirectURI;
+  nsresult rv;
   nsCOMPtr<nsIHttpChannel> newHttpChannel =
       do_QueryInterface(mRedirectChannelChild);
 
@@ -1697,18 +1697,9 @@ HttpChannelChild::OnRedirectVerifyCallback(nsresult result)
     result = NS_ERROR_DOM_BAD_URI;
   }
 
-  bool forceHSTSPriming = false;
-  bool mixedContentWouldBlock = false;
   if (newHttpChannel) {
     // Must not be called until after redirect observers called.
     newHttpChannel->SetOriginalURI(mOriginalURI);
-
-    nsCOMPtr<nsILoadInfo> newLoadInfo;
-    rv = newHttpChannel->GetLoadInfo(getter_AddRefs(newLoadInfo));
-    if (NS_SUCCEEDED(rv) && newLoadInfo) {
-      forceHSTSPriming = newLoadInfo->GetForceHSTSPriming();
-      mixedContentWouldBlock = newLoadInfo->GetMixedContentWouldBlock();
-    }
   }
 
   if (mRedirectingForSubsequentSynthesizedResponse) {
@@ -1756,7 +1747,7 @@ HttpChannelChild::OnRedirectVerifyCallback(nsresult result)
       do_QueryInterface(mRedirectChannelChild);
     if (newHttpChannelInternal) {
       nsCOMPtr<nsIURI> apiRedirectURI;
-      nsresult rv = newHttpChannelInternal->GetApiRedirectToURI(
+      rv = newHttpChannelInternal->GetApiRedirectToURI(
         getter_AddRefs(apiRedirectURI));
       if (NS_SUCCEEDED(rv) && apiRedirectURI) {
         /* If there was an API redirect of this channel, we need to send it
@@ -1780,8 +1771,7 @@ HttpChannelChild::OnRedirectVerifyCallback(nsresult result)
 
   if (mIPCOpen)
     SendRedirect2Verify(result, *headerTuples, loadFlags, redirectURI,
-                        corsPreflightArgs, forceHSTSPriming,
-                        mixedContentWouldBlock, chooseAppcache);
+                        corsPreflightArgs, chooseAppcache);
 
   return NS_OK;
 }
diff --git a/netwerk/protocol/http/HttpChannelParent.cpp b/netwerk/protocol/http/HttpChannelParent.cpp
index 90ed597a6..d1c67f01b 100644
--- a/netwerk/protocol/http/HttpChannelParent.cpp
+++ b/netwerk/protocol/http/HttpChannelParent.cpp
@@ -733,8 +733,6 @@ HttpChannelParent::RecvRedirect2Verify(const nsresult& result,
                                        const uint32_t& loadFlags,
                                        const OptionalURIParams& aAPIRedirectURI,
                                        const OptionalCorsPreflightArgs& aCorsPreflightArgs,
-                                       const bool& aForceHSTSPriming,
-                                       const bool& aMixedContentWouldBlock,
                                        const bool& aChooseAppcache)
 {
   LOG(("HttpChannelParent::RecvRedirect2Verify [this=%p result=%x]\n",
@@ -774,14 +772,6 @@ HttpChannelParent::RecvRedirect2Verify(const nsresult& result,
         newInternalChannel->SetCorsPreflightParameters(args.unsafeHeaders());
       }
 
-      if (aForceHSTSPriming) {
-        nsCOMPtr<nsILoadInfo> newLoadInfo;
-        rv = newHttpChannel->GetLoadInfo(getter_AddRefs(newLoadInfo));
-        if (NS_SUCCEEDED(rv) && newLoadInfo) {
-          newLoadInfo->SetHSTSPriming(aMixedContentWouldBlock);
-        }
-      }
-
       nsCOMPtr<nsIApplicationCacheChannel> appCacheChannel =
         do_QueryInterface(newHttpChannel);
       if (appCacheChannel) {
diff --git a/netwerk/protocol/http/HttpChannelParent.h b/netwerk/protocol/http/HttpChannelParent.h
index 56854bb55..91f9bac8b 100644
--- a/netwerk/protocol/http/HttpChannelParent.h
+++ b/netwerk/protocol/http/HttpChannelParent.h
@@ -162,8 +162,6 @@ protected:
                                    const uint32_t& loadFlags,
                                    const OptionalURIParams& apiRedirectUri,
                                    const OptionalCorsPreflightArgs& aCorsPreflightArgs,
-                                   const bool& aForceHSTSPriming,
-                                   const bool& aMixedContentWouldBlock,
                                    const bool& aChooseAppcache) override;
   virtual bool RecvUpdateAssociatedContentSecurity(const int32_t& broken,
                                                    const int32_t& no) override;
diff --git a/netwerk/protocol/http/PHttpChannel.ipdl b/netwerk/protocol/http/PHttpChannel.ipdl
index 1eb25a403..c77a53e40 100644
--- a/netwerk/protocol/http/PHttpChannel.ipdl
+++ b/netwerk/protocol/http/PHttpChannel.ipdl
@@ -47,7 +47,6 @@ parent:
   async Redirect2Verify(nsresult result, RequestHeaderTuples changedHeaders,
                         uint32_t loadFlags, OptionalURIParams apiRedirectTo,
                         OptionalCorsPreflightArgs corsPreflightArgs,
-                        bool forceHSTSPriming, bool mixedContentWouldBlock,
                         bool chooseAppcache);
 
   // For document loads we keep this protocol open after child's
diff --git a/netwerk/protocol/http/moz.build b/netwerk/protocol/http/moz.build
index e13101aa0..1368ee707 100644
--- a/netwerk/protocol/http/moz.build
+++ b/netwerk/protocol/http/moz.build
@@ -5,7 +5,6 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 XPIDL_SOURCES += [
-    'nsIHstsPrimingCallback.idl',
     'nsIHttpActivityObserver.idl',
     'nsIHttpAuthenticableChannel.idl',
     'nsIHttpAuthenticator.idl',
@@ -58,7 +57,6 @@ UNIFIED_SOURCES += [
     'AltDataOutputStreamParent.cpp',
     'CacheControlParser.cpp',
     'ConnectionDiagnostics.cpp',
-    'HSTSPrimerListener.cpp',
     'Http2Compression.cpp',
     'Http2Push.cpp',
     'Http2Session.cpp',
diff --git a/netwerk/protocol/http/nsHttpChannel.cpp b/netwerk/protocol/http/nsHttpChannel.cpp
index 9107b16e8..7bcec146d 100644
--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -100,7 +100,6 @@
 #include "mozilla/net/Predictor.h"
 #include "CacheControlParser.h"
 #include "nsMixedContentBlocker.h"
-#include "HSTSPrimerListener.h"
 #include "CacheStorageService.h"
 
 namespace mozilla { namespace net {
@@ -465,50 +464,12 @@ nsHttpChannel::Connect()
         // otherwise, let's just proceed without using the cache.
     }
 
-    return TryHSTSPriming();
-}
-
-nsresult
-nsHttpChannel::TryHSTSPriming()
-{
-    if (mLoadInfo) {
-        // HSTS priming requires the LoadInfo provided with AsyncOpen2
-        bool requireHSTSPriming =
-            mLoadInfo->GetForceHSTSPriming();
-
-        if (requireHSTSPriming &&
-                nsMixedContentBlocker::sSendHSTSPriming &&
-                mInterceptCache == DO_NOT_INTERCEPT) {
-            bool isHttpsScheme;
-            nsresult rv = mURI->SchemeIs("https", &isHttpsScheme);
-            NS_ENSURE_SUCCESS(rv, rv);
-            if (!isHttpsScheme) {
-                rv = HSTSPrimingListener::StartHSTSPriming(this, this);
-
-                if (NS_FAILED(rv)) {
-                    CloseCacheEntry(false);
-                    return rv;
-                }
-
-                return NS_OK;
-            }
-
-            // The request was already upgraded, for example by
-            // upgrade-insecure-requests or a prior successful priming request
-            Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                    HSTSPrimingResult::eHSTS_PRIMING_ALREADY_UPGRADED);
-            mLoadInfo->ClearHSTSPriming();
-        }
-    }
-
     return ContinueConnect();
 }
 
 nsresult
 nsHttpChannel::ContinueConnect()
 {
-    // If we have had HSTS priming, we need to reevaluate whether we need
-    // a CORS preflight. Bug: 1272440
     // If we need to start a CORS preflight, do it now!
     // Note that it is important to do this before the early returns below.
     if (!mIsCorsPreflightDone && mRequireCORSPreflight &&
@@ -4283,7 +4244,7 @@ nsHttpChannel::OnCacheEntryAvailableInternal(nsICacheEntry *entry,
         return NS_OK;
     }
 
-    return TryHSTSPriming();
+    return ContinueConnect();
 }
 
 nsresult
@@ -5699,7 +5660,6 @@ NS_INTERFACE_MAP_BEGIN(nsHttpChannel)
     NS_INTERFACE_MAP_ENTRY(nsIDNSListener)
     NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
     NS_INTERFACE_MAP_ENTRY(nsICorsPreflightCallback)
-    NS_INTERFACE_MAP_ENTRY(nsIHstsPrimingCallback)
     NS_INTERFACE_MAP_ENTRY(nsIChannelWithDivertableParentListener)
     // we have no macro that covers this case.
     if (aIID.Equals(NS_GET_IID(nsHttpChannel)) ) {
@@ -8186,107 +8146,6 @@ nsHttpChannel::OnPreflightFailed(nsresult aError)
 }
 
 //-----------------------------------------------------------------------------
-// nsIHstsPrimingCallback functions
-//-----------------------------------------------------------------------------
-
-/*
- * May be invoked synchronously if HSTS priming has already been performed
- * for the host.
- */
-nsresult
-nsHttpChannel::OnHSTSPrimingSucceeded(bool aCached)
-{
-    if (nsMixedContentBlocker::sUseHSTS) {
-        // redirect the channel to HTTPS if the pref
-        // "security.mixed_content.use_hsts" is true
-        LOG(("HSTS Priming succeeded, redirecting to HTTPS [this=%p]", this));
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                (aCached) ? HSTSPrimingResult::eHSTS_PRIMING_CACHED_DO_UPGRADE :
-                            HSTSPrimingResult::eHSTS_PRIMING_SUCCEEDED);
-        return AsyncCall(&nsHttpChannel::HandleAsyncRedirectChannelToHttps);
-    }
-
-    // If "security.mixed_content.use_hsts" is false, record the result of
-    // HSTS priming and block or proceed with the load as required by
-    // mixed-content blocking
-    bool wouldBlock = mLoadInfo->GetMixedContentWouldBlock();
-
-    // preserve the mixed-content-before-hsts order and block if required
-    if (wouldBlock) {
-        LOG(("HSTS Priming succeeded, blocking for mixed-content [this=%p]",
-                    this));
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                              HSTSPrimingResult::eHSTS_PRIMING_SUCCEEDED_BLOCK);
-        CloseCacheEntry(false);
-        return AsyncAbort(NS_ERROR_CONTENT_BLOCKED);
-    }
-
-    LOG(("HSTS Priming succeeded, loading insecure: [this=%p]", this));
-    Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                          HSTSPrimingResult::eHSTS_PRIMING_SUCCEEDED_HTTP);
-
-    nsresult rv = ContinueConnect();
-    if (NS_FAILED(rv)) {
-        CloseCacheEntry(false);
-        return AsyncAbort(rv);
-    }
-
-    return NS_OK;
-}
-
-/*
- * May be invoked synchronously if HSTS priming has already been performed
- * for the host.
- */
-nsresult
-nsHttpChannel::OnHSTSPrimingFailed(nsresult aError, bool aCached)
-{
-    bool wouldBlock = mLoadInfo->GetMixedContentWouldBlock();
-
-    LOG(("HSTS Priming Failed [this=%p], %s the load", this,
-                (wouldBlock) ? "blocking" : "allowing"));
-    if (aCached) {
-        // Between the time we marked for priming and started the priming request,
-        // the host was found to not allow the upgrade, probably from another
-        // priming request.
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                (wouldBlock) ?  HSTSPrimingResult::eHSTS_PRIMING_CACHED_BLOCK :
-                                HSTSPrimingResult::eHSTS_PRIMING_CACHED_NO_UPGRADE);
-    } else {
-        // A priming request was sent, and no HSTS header was found that allows
-        // the upgrade.
-        Telemetry::Accumulate(Telemetry::MIXED_CONTENT_HSTS_PRIMING_RESULT,
-                (wouldBlock) ?  HSTSPrimingResult::eHSTS_PRIMING_FAILED_BLOCK :
-                                HSTSPrimingResult::eHSTS_PRIMING_FAILED_ACCEPT);
-    }
-
-    // Don't visit again for at least
-    // security.mixed_content.hsts_priming_cache_timeout seconds.
-    nsISiteSecurityService* sss = gHttpHandler->GetSSService();
-    NS_ENSURE_TRUE(sss, NS_ERROR_OUT_OF_MEMORY);
-    nsresult rv = sss->CacheNegativeHSTSResult(mURI,
-            nsMixedContentBlocker::sHSTSPrimingCacheTimeout);
-    if (NS_FAILED(rv)) {
-        NS_ERROR("nsISiteSecurityService::CacheNegativeHSTSResult failed");
-    }
-
-    // If we would block, go ahead and abort with the error provided
-    if (wouldBlock) {
-        CloseCacheEntry(false);
-        return AsyncAbort(aError);
-    }
-
-    // we can continue the load and the UI has been updated as mixed content
-    rv = ContinueConnect();
-    if (NS_FAILED(rv)) {
-        CloseCacheEntry(false);
-        return AsyncAbort(rv);
-    }
-
-    return NS_OK;
-}
-
-//-----------------------------------------------------------------------------
 // AChannelHasDivertableParentChannelAsListener internal functions
 //-----------------------------------------------------------------------------
 
diff --git a/netwerk/protocol/http/nsHttpChannel.h b/netwerk/protocol/http/nsHttpChannel.h
index cb8925d04..3a322e8e2 100644
--- a/netwerk/protocol/http/nsHttpChannel.h
+++ b/netwerk/protocol/http/nsHttpChannel.h
@@ -28,7 +28,6 @@
 #include "nsISupportsPrimitives.h"
 #include "nsICorsPreflightCallback.h"
 #include "AlternateServices.h"
-#include "nsIHstsPrimingCallback.h"
 
 class nsDNSPrefetch;
 class nsICancelable;
@@ -76,7 +75,6 @@ class nsHttpChannel final : public HttpBaseChannel
                           , public nsSupportsWeakReference
                           , public nsICorsPreflightCallback
                           , public nsIChannelWithDivertableParentListener
-                          , public nsIHstsPrimingCallback
 {
 public:
     NS_DECL_ISUPPORTS_INHERITED
@@ -92,7 +90,6 @@ public:
     NS_DECL_NSIAPPLICATIONCACHECONTAINER
     NS_DECL_NSIAPPLICATIONCACHECHANNEL
     NS_DECL_NSIASYNCVERIFYREDIRECTCALLBACK
-    NS_DECL_NSIHSTSPRIMINGCALLBACK
     NS_DECL_NSITHREADRETARGETABLEREQUEST
     NS_DECL_NSIDNSLISTENER
     NS_DECL_NSICHANNELWITHDIVERTABLEPARENTLISTENER
@@ -211,9 +208,6 @@ public: /* internal necko use only */
     nsresult OpenCacheEntry(bool usingSSL);
     nsresult ContinueConnect();
 
-    // If the load is mixed-content, build and send an HSTS priming request.
-    nsresult TryHSTSPriming();
-
     nsresult StartRedirectChannelToURI(nsIURI *, uint32_t);
 
     // This allows cache entry to be marked as foreign even after channel itself
diff --git a/netwerk/protocol/http/nsIHstsPrimingCallback.idl b/netwerk/protocol/http/nsIHstsPrimingCallback.idl
deleted file mode 100644
index 01f53a5b2..000000000
--- a/netwerk/protocol/http/nsIHstsPrimingCallback.idl
+++ /dev/null
@@ -1,50 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-/**
- * HSTS priming attempts to prevent mixed-content by looking for the
- * Strict-Transport-Security header as a signal from the server that it is
- * safe to upgrade HTTP to HTTPS.
- *
- * Since mixed-content blocking happens very early in the process in AsyncOpen2,
- * the status of mixed-content blocking is stored in the LoadInfo and then used
- * to determine whether to send a priming request or not.
- *
- * This interface is implemented by nsHttpChannel so that it can receive the
- * result of HSTS priming.
- */
-[builtinclass, uuid(eca6daca-3f2a-4a2a-b3bf-9f24f79bc999)]
-interface nsIHstsPrimingCallback : nsISupports
-{
-  /**
-   * HSTS priming has succeeded with an STS header, and the site asserts it is
-   * safe to upgrade the request from HTTP to HTTPS. The request may still be
-   * blocked based on the user's preferences.
-   *
-   * May be invoked synchronously if HSTS priming has already been performed
-   * for the host.
-   *
-   * @param aCached whether the result was already in the HSTS cache
-   */
-  [noscript, nostdcall]
-  void onHSTSPrimingSucceeded(in bool aCached);
-  /**
-   * HSTS priming has seen no STS header, the request itself has failed,
-   * or some other failure which does not constitute a positive signal that the
-   * site can be upgraded safely to HTTPS. The request may still be allowed
-   * based on the user's preferences.
-   *
-   * May be invoked synchronously if HSTS priming has already been performed
-   * for the host.
-   *
-   * @param aError The error which caused this failure, or NS_ERROR_CONTENT_BLOCKED
-   * @param aCached whether the result was already in the HSTS cache
-   */
-  [noscript, nostdcall]
-  void onHSTSPrimingFailed(in nsresult aError, in bool aCached);
-};
diff --git a/security/manager/ssl/nsISiteSecurityService.idl b/security/manager/ssl/nsISiteSecurityService.idl
index fa20fe307..753f32b57 100644
--- a/security/manager/ssl/nsISiteSecurityService.idl
+++ b/security/manager/ssl/nsISiteSecurityService.idl
@@ -188,15 +188,6 @@ interface nsISiteSecurityService : nsISupports
                         in int64_t aExpires, in unsigned long aPinCount,
                         [array, size_is(aPinCount)] in string aSha256Pins,
                         [optional] in boolean aIsPreload);
-
-    /**
-     * Mark a host as declining to provide a given security state so that features
-     * such as HSTS priming will not flood a server with requests.
-     *
-     * @param aURI the nsIURI that this applies to
-     * @param aMaxAge lifetime (in seconds) of this negative cache
-     */
-    [noscript] void cacheNegativeHSTSResult(in nsIURI aURI, in unsigned long long aMaxAge);
 };
 
 %{C++
diff --git a/security/manager/ssl/nsSiteSecurityService.cpp b/security/manager/ssl/nsSiteSecurityService.cpp
index 322ef6570..d461f6b61 100644
--- a/security/manager/ssl/nsSiteSecurityService.cpp
+++ b/security/manager/ssl/nsSiteSecurityService.cpp
@@ -356,14 +356,6 @@ nsSiteSecurityService::SetHSTSState(uint32_t aType,
 }
 
 NS_IMETHODIMP
-nsSiteSecurityService::CacheNegativeHSTSResult(nsIURI* aSourceURI,
-                                               uint64_t aMaxAge)
-{
-  return SetHSTSState(nsISiteSecurityService::HEADER_HSTS, aSourceURI,
-                      aMaxAge, false, 0, SecurityPropertyNegative);
-}
-
-NS_IMETHODIMP
 nsSiteSecurityService::RemoveState(uint32_t aType, nsIURI* aURI,
                                    uint32_t aFlags)
 {
diff --git a/testing/runtimes/mochitest-browser-chrome-e10s.runtimes.json b/testing/runtimes/mochitest-browser-chrome-e10s.runtimes.json
index 5c97d58f0..211e98e05 100644
--- a/testing/runtimes/mochitest-browser-chrome-e10s.runtimes.json
+++ b/testing/runtimes/mochitest-browser-chrome-e10s.runtimes.json
@@ -648,13 +648,6 @@
     "dom/security/test/contentverifier/browser_verify_content_about_newtab.js": 14195, 
     "dom/security/test/contentverifier/browser_verify_content_about_newtab2.js": 12159, 
     "dom/security/test/csp/browser_test_web_manifest.js": 6022, 
-    "dom/security/test/hsts/browser_hsts-priming_allow_active.js": 2840, 
-    "dom/security/test/hsts/browser_hsts-priming_block_active.js": 3459, 
-    "dom/security/test/hsts/browser_hsts-priming_block_active_with_redir_same.js": 3233, 
-    "dom/security/test/hsts/browser_hsts-priming_cache-timeout.js": 3469, 
-    "dom/security/test/hsts/browser_hsts-priming_hsts_after_mixed.js": 2658, 
-    "dom/security/test/hsts/browser_hsts-priming_no-duplicates.js": 3793, 
-    "dom/security/test/hsts/browser_hsts-priming_timeout.js": 4040, 
     "dom/tests/browser/browser_ConsoleStoragePBTest_perwindowpb.js": 3659, 
     "dom/tests/browser/browser_bug396843.js": 6574, 
     "dom/tests/browser/browser_focus_steal_from_chrome.js": 25508, 
diff --git a/testing/runtimes/mochitest-browser-chrome.runtimes.json b/testing/runtimes/mochitest-browser-chrome.runtimes.json
index ac0b9f10d..73b2437a2 100644
--- a/testing/runtimes/mochitest-browser-chrome.runtimes.json
+++ b/testing/runtimes/mochitest-browser-chrome.runtimes.json
@@ -621,14 +621,6 @@
     "dom/security/test/contentverifier/browser_verify_content_about_newtab2.js": 10284, 
     "dom/security/test/csp/browser_manifest-src-override-default-src.js": 1939, 
     "dom/security/test/csp/browser_test_web_manifest.js": 5639, 
-    "dom/security/test/hsts/browser_hsts-priming_allow_active.js": 2280, 
-    "dom/security/test/hsts/browser_hsts-priming_allow_display.js": 1974, 
-    "dom/security/test/hsts/browser_hsts-priming_block_active.js": 2803, 
-    "dom/security/test/hsts/browser_hsts-priming_block_active_with_redir_same.js": 2682, 
-    "dom/security/test/hsts/browser_hsts-priming_cache-timeout.js": 3110, 
-    "dom/security/test/hsts/browser_hsts-priming_hsts_after_mixed.js": 2328, 
-    "dom/security/test/hsts/browser_hsts-priming_no-duplicates.js": 2831, 
-    "dom/security/test/hsts/browser_hsts-priming_timeout.js": 3798, 
     "dom/tests/browser/browser_ConsoleAPITests.js": 3520, 
     "dom/tests/browser/browser_ConsoleStoragePBTest_perwindowpb.js": 2914, 
     "dom/tests/browser/browser_bug396843.js": 6050, 
diff --git a/toolkit/components/telemetry/Histograms.json b/toolkit/components/telemetry/Histograms.json
index ade308cfa..82597adec 100644
--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -8312,33 +8312,6 @@
     "n_values": 10,
     "description": "How often would blocked mixed content be allowed if HSTS upgrades were allowed? 0=display/no-HSTS, 1=display/HSTS, 2=active/no-HSTS, 3=active/HSTS"
   },
-  "MIXED_CONTENT_HSTS_PRIMING": {
-    "alert_emails": ["seceng@mozilla.org"],
-    "bug_numbers": [1246540],
-    "expires_in_version": "60",
-    "kind": "enumerated",
-    "n_values": 16,
-    "description": "How often would blocked mixed content be allowed if HSTS upgrades were allowed, including how often would we send an HSTS priming request? 0=display/no-HSTS, 1=display/HSTS, 2=active/no-HSTS, 3=active/HSTS, 4=display/no-HSTS-priming, 5=display/do-HSTS-priming, 6=active/no-HSTS-priming, 7=active/do-HSTS-priming"
-  },
-  "MIXED_CONTENT_HSTS_PRIMING_RESULT": {
-    "alert_emails": ["seceng@mozilla.org"],
-    "bug_numbers": [1246540],
-    "expires_in_version": "60",
-    "kind": "enumerated",
-    "n_values": 16,
-    "description": "How often do we get back an HSTS priming result which upgrades the connection to HTTPS? 0=cached (no upgrade), 1=cached (do upgrade), 2=cached (blocked), 3=already upgraded, 4=priming succeeded, 5=priming succeeded (block due to pref), 6=priming succeeded (no upgrade due to pref), 7=priming failed (block), 8=priming failed (accept)"
-  },
-  "HSTS_PRIMING_REQUEST_DURATION": {
-    "alert_emails": ["seceng-telemetry@mozilla.org"],
-    "bug_numbers": [1311893],
-    "expires_in_version": "58",
-    "kind": "exponential",
-    "low": 100,
-    "high": 30000,
-    "n_buckets": 100,
-    "keyed": true,
-    "description": "The amount of time required for HSTS priming requests (ms), keyed by success or failure of the priming request. (success, failure)"
-  },
   "MIXED_CONTENT_OBJECT_SUBREQUEST": {
     "alert_emails": ["seceng@mozilla.org"],
     "bug_numbers": [1244116],