Add m-esr52 at 52.6.0

1 files changed, 2550 insertions, 0 deletions

diff --git a/netwerk/base/Predictor.cpp b/netwerk/base/Predictor.cpp
new file mode 100644
index 000000000..e97b11d16
--- /dev/null
+++ b/netwerk/base/Predictor.cpp
@@ -0,0 +1,2550 @@
+/* vim: set ts=2 sts=2 et sw=2: */
+/* 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 <algorithm>
+
+#include "Predictor.h"
+
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsICacheStorage.h"
+#include "nsICacheStorageService.h"
+#include "nsICachingChannel.h"
+#include "nsICancelable.h"
+#include "nsIChannel.h"
+#include "nsContentUtils.h"
+#include "nsIDNSService.h"
+#include "nsIDocument.h"
+#include "nsIFile.h"
+#include "nsIHttpChannel.h"
+#include "nsIInputStream.h"
+#include "nsIIOService.h"
+#include "nsILoadContext.h"
+#include "nsILoadContextInfo.h"
+#include "nsILoadGroup.h"
+#include "nsINetworkPredictorVerifier.h"
+#include "nsIObserverService.h"
+#include "nsIPrefBranch.h"
+#include "nsIPrefService.h"
+#include "nsISpeculativeConnect.h"
+#include "nsITimer.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+#include "nsServiceManagerUtils.h"
+#include "nsStreamUtils.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "mozilla/Logging.h"
+
+#include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
+
+#include "mozilla/net/NeckoCommon.h"
+#include "mozilla/net/NeckoParent.h"
+
+#include "LoadContextInfo.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "SerializedLoadContext.h"
+#include "mozilla/net/NeckoChild.h"
+
+#include "mozilla/dom/ContentParent.h"
+
+using namespace mozilla;
+
+namespace mozilla {
+namespace net {
+
+Predictor *Predictor::sSelf = nullptr;
+
+static LazyLogModule gPredictorLog("NetworkPredictor");
+
+#define PREDICTOR_LOG(args) MOZ_LOG(gPredictorLog, mozilla::LogLevel::Debug, args)
+
+#define RETURN_IF_FAILED(_rv) \
+  do { \
+    if (NS_FAILED(_rv)) { \
+      return; \
+    } \
+  } while (0)
+
+#define NOW_IN_SECONDS() static_cast<uint32_t>(PR_Now() / PR_USEC_PER_SEC)
+
+
+static const char PREDICTOR_ENABLED_PREF[] = "network.predictor.enabled";
+static const char PREDICTOR_SSL_HOVER_PREF[] = "network.predictor.enable-hover-on-ssl";
+static const char PREDICTOR_PREFETCH_PREF[] = "network.predictor.enable-prefetch";
+
+static const char PREDICTOR_PAGE_DELTA_DAY_PREF[] =
+  "network.predictor.page-degradation.day";
+static const int32_t PREDICTOR_PAGE_DELTA_DAY_DEFAULT = 0;
+static const char PREDICTOR_PAGE_DELTA_WEEK_PREF[] =
+  "network.predictor.page-degradation.week";
+static const int32_t PREDICTOR_PAGE_DELTA_WEEK_DEFAULT = 5;
+static const char PREDICTOR_PAGE_DELTA_MONTH_PREF[] =
+  "network.predictor.page-degradation.month";
+static const int32_t PREDICTOR_PAGE_DELTA_MONTH_DEFAULT = 10;
+static const char PREDICTOR_PAGE_DELTA_YEAR_PREF[] =
+  "network.predictor.page-degradation.year";
+static const int32_t PREDICTOR_PAGE_DELTA_YEAR_DEFAULT = 25;
+static const char PREDICTOR_PAGE_DELTA_MAX_PREF[] =
+  "network.predictor.page-degradation.max";
+static const int32_t PREDICTOR_PAGE_DELTA_MAX_DEFAULT = 50;
+static const char PREDICTOR_SUB_DELTA_DAY_PREF[] =
+  "network.predictor.subresource-degradation.day";
+static const int32_t PREDICTOR_SUB_DELTA_DAY_DEFAULT = 1;
+static const char PREDICTOR_SUB_DELTA_WEEK_PREF[] =
+  "network.predictor.subresource-degradation.week";
+static const int32_t PREDICTOR_SUB_DELTA_WEEK_DEFAULT = 10;
+static const char PREDICTOR_SUB_DELTA_MONTH_PREF[] =
+  "network.predictor.subresource-degradation.month";
+static const int32_t PREDICTOR_SUB_DELTA_MONTH_DEFAULT = 25;
+static const char PREDICTOR_SUB_DELTA_YEAR_PREF[] =
+  "network.predictor.subresource-degradation.year";
+static const int32_t PREDICTOR_SUB_DELTA_YEAR_DEFAULT = 50;
+static const char PREDICTOR_SUB_DELTA_MAX_PREF[] =
+  "network.predictor.subresource-degradation.max";
+static const int32_t PREDICTOR_SUB_DELTA_MAX_DEFAULT = 100;
+
+static const char PREDICTOR_PREFETCH_ROLLING_LOAD_PREF[] =
+  "network.predictor.prefetch-rolling-load-count";
+static const int32_t PREFETCH_ROLLING_LOAD_DEFAULT = 10;
+static const char PREDICTOR_PREFETCH_MIN_PREF[] =
+  "network.predictor.prefetch-min-confidence";
+static const int32_t PREFETCH_MIN_DEFAULT = 100;
+static const char PREDICTOR_PRECONNECT_MIN_PREF[] =
+  "network.predictor.preconnect-min-confidence";
+static const int32_t PRECONNECT_MIN_DEFAULT = 90;
+static const char PREDICTOR_PRERESOLVE_MIN_PREF[] =
+  "network.predictor.preresolve-min-confidence";
+static const int32_t PRERESOLVE_MIN_DEFAULT = 60;
+static const char PREDICTOR_REDIRECT_LIKELY_PREF[] =
+  "network.predictor.redirect-likely-confidence";
+static const int32_t REDIRECT_LIKELY_DEFAULT = 75;
+
+static const char PREDICTOR_PREFETCH_FORCE_VALID_PREF[] =
+  "network.predictor.prefetch-force-valid-for";
+static const int32_t PREFETCH_FORCE_VALID_DEFAULT = 10;
+
+static const char PREDICTOR_MAX_RESOURCES_PREF[] =
+  "network.predictor.max-resources-per-entry";
+static const uint32_t PREDICTOR_MAX_RESOURCES_DEFAULT = 100;
+
+// This is selected in concert with max-resources-per-entry to keep memory usage
+// low-ish. The default of the combo of the two is ~50k
+static const char PREDICTOR_MAX_URI_LENGTH_PREF[] =
+  "network.predictor.max-uri-length";
+static const uint32_t PREDICTOR_MAX_URI_LENGTH_DEFAULT = 500;
+
+static const char PREDICTOR_DOING_TESTS_PREF[] = "network.predictor.doing-tests";
+
+static const char PREDICTOR_CLEANED_UP_PREF[] = "network.predictor.cleaned-up";
+
+// All these time values are in sec
+static const uint32_t ONE_DAY = 86400U;
+static const uint32_t ONE_WEEK = 7U * ONE_DAY;
+static const uint32_t ONE_MONTH = 30U * ONE_DAY;
+static const uint32_t ONE_YEAR = 365U * ONE_DAY;
+
+static const uint32_t STARTUP_WINDOW = 5U * 60U; // 5min
+
+// Version of metadata entries we expect
+static const uint32_t METADATA_VERSION = 1;
+
+// Flags available in entries
+// FLAG_PREFETCHABLE - we have determined that this item is eligible for prefetch
+static const uint32_t FLAG_PREFETCHABLE = 1 << 0;
+
+// We save 12 bits in the "flags" section of our metadata for actual flags, the
+// rest are to keep track of a rolling count of which loads a resource has been
+// used on to determine if we can prefetch that resource or not;
+static const uint8_t kRollingLoadOffset = 12;
+static const int32_t kMaxPrefetchRollingLoadCount = 20;
+static const uint32_t kFlagsMask = ((1 << kRollingLoadOffset) - 1);
+
+// ID Extensions for cache entries
+#define PREDICTOR_ORIGIN_EXTENSION "predictor-origin"
+
+// Get the full origin (scheme, host, port) out of a URI (maybe should be part
+// of nsIURI instead?)
+static nsresult
+ExtractOrigin(nsIURI *uri, nsIURI **originUri, nsIIOService *ioService)
+{
+  nsAutoCString s;
+  s.Truncate();
+  nsresult rv = nsContentUtils::GetASCIIOrigin(uri, s);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_NewURI(originUri, s, nullptr, nullptr, ioService);
+}
+
+// All URIs we get passed *must* be http or https if they're not null. This
+// helps ensure that.
+static bool
+IsNullOrHttp(nsIURI *uri)
+{
+  if (!uri) {
+    return true;
+  }
+
+  bool isHTTP = false;
+  uri->SchemeIs("http", &isHTTP);
+  if (!isHTTP) {
+    uri->SchemeIs("https", &isHTTP);
+  }
+
+  return isHTTP;
+}
+
+// Listener for the speculative DNS requests we'll fire off, which just ignores
+// the result (since we're just trying to warm the cache). This also exists to
+// reduce round-trips to the main thread, by being something threadsafe the
+// Predictor can use.
+
+NS_IMPL_ISUPPORTS(Predictor::DNSListener, nsIDNSListener);
+
+NS_IMETHODIMP
+Predictor::DNSListener::OnLookupComplete(nsICancelable *request,
+                                         nsIDNSRecord *rec,
+                                         nsresult status)
+{
+  return NS_OK;
+}
+
+// Class to proxy important information from the initial predictor call through
+// the cache API and back into the internals of the predictor. We can't use the
+// predictor itself, as it may have multiple actions in-flight, and each action
+// has different parameters.
+NS_IMPL_ISUPPORTS(Predictor::Action, nsICacheEntryOpenCallback);
+
+Predictor::Action::Action(bool fullUri, bool predict,
+                          Predictor::Reason reason,
+                          nsIURI *targetURI, nsIURI *sourceURI,
+                          nsINetworkPredictorVerifier *verifier,
+                          Predictor *predictor)
+  :mFullUri(fullUri)
+  ,mPredict(predict)
+  ,mTargetURI(targetURI)
+  ,mSourceURI(sourceURI)
+  ,mVerifier(verifier)
+  ,mStackCount(0)
+  ,mPredictor(predictor)
+{
+  mStartTime = TimeStamp::Now();
+  if (mPredict) {
+    mPredictReason = reason.mPredict;
+  } else {
+    mLearnReason = reason.mLearn;
+  }
+}
+
+Predictor::Action::Action(bool fullUri, bool predict,
+                          Predictor::Reason reason,
+                          nsIURI *targetURI, nsIURI *sourceURI,
+                          nsINetworkPredictorVerifier *verifier,
+                          Predictor *predictor, uint8_t stackCount)
+  :mFullUri(fullUri)
+  ,mPredict(predict)
+  ,mTargetURI(targetURI)
+  ,mSourceURI(sourceURI)
+  ,mVerifier(verifier)
+  ,mStackCount(stackCount)
+  ,mPredictor(predictor)
+{
+  mStartTime = TimeStamp::Now();
+  if (mPredict) {
+    mPredictReason = reason.mPredict;
+  } else {
+    mLearnReason = reason.mLearn;
+  }
+}
+
+Predictor::Action::~Action()
+{ }
+
+NS_IMETHODIMP
+Predictor::Action::OnCacheEntryCheck(nsICacheEntry *entry,
+                                     nsIApplicationCache *appCache,
+                                     uint32_t *result)
+{
+  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Action::OnCacheEntryAvailable(nsICacheEntry *entry, bool isNew,
+                                         nsIApplicationCache *appCache,
+                                         nsresult result)
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Got cache entry off main thread!");
+
+  nsAutoCString targetURI, sourceURI;
+  mTargetURI->GetAsciiSpec(targetURI);
+  if (mSourceURI) {
+    mSourceURI->GetAsciiSpec(sourceURI);
+  }
+  PREDICTOR_LOG(("OnCacheEntryAvailable %p called. entry=%p mFullUri=%d mPredict=%d "
+                 "mPredictReason=%d mLearnReason=%d mTargetURI=%s "
+                 "mSourceURI=%s mStackCount=%d isNew=%d result=0x%08x",
+                 this, entry, mFullUri, mPredict, mPredictReason, mLearnReason,
+                 targetURI.get(), sourceURI.get(), mStackCount,
+                 isNew, result));
+  if (NS_FAILED(result)) {
+    PREDICTOR_LOG(("OnCacheEntryAvailable %p FAILED to get cache entry (0x%08X). "
+                   "Aborting.", this, result));
+    return NS_OK;
+  }
+  Telemetry::AccumulateTimeDelta(Telemetry::PREDICTOR_WAIT_TIME,
+                                 mStartTime);
+  if (mPredict) {
+    bool predicted = mPredictor->PredictInternal(mPredictReason, entry, isNew,
+                                                 mFullUri, mTargetURI,
+                                                 mVerifier, mStackCount);
+    Telemetry::AccumulateTimeDelta(
+      Telemetry::PREDICTOR_PREDICT_WORK_TIME, mStartTime);
+    if (predicted) {
+      Telemetry::AccumulateTimeDelta(
+        Telemetry::PREDICTOR_PREDICT_TIME_TO_ACTION, mStartTime);
+    } else {
+      Telemetry::AccumulateTimeDelta(
+        Telemetry::PREDICTOR_PREDICT_TIME_TO_INACTION, mStartTime);
+    }
+  } else {
+    mPredictor->LearnInternal(mLearnReason, entry, isNew, mFullUri, mTargetURI,
+                              mSourceURI);
+    Telemetry::AccumulateTimeDelta(
+      Telemetry::PREDICTOR_LEARN_WORK_TIME, mStartTime);
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(Predictor,
+                  nsINetworkPredictor,
+                  nsIObserver,
+                  nsISpeculativeConnectionOverrider,
+                  nsIInterfaceRequestor,
+                  nsICacheEntryMetaDataVisitor,
+                  nsINetworkPredictorVerifier)
+
+Predictor::Predictor()
+  :mInitialized(false)
+  ,mEnabled(true)
+  ,mEnableHoverOnSSL(false)
+  ,mEnablePrefetch(true)
+  ,mPageDegradationDay(PREDICTOR_PAGE_DELTA_DAY_DEFAULT)
+  ,mPageDegradationWeek(PREDICTOR_PAGE_DELTA_WEEK_DEFAULT)
+  ,mPageDegradationMonth(PREDICTOR_PAGE_DELTA_MONTH_DEFAULT)
+  ,mPageDegradationYear(PREDICTOR_PAGE_DELTA_YEAR_DEFAULT)
+  ,mPageDegradationMax(PREDICTOR_PAGE_DELTA_MAX_DEFAULT)
+  ,mSubresourceDegradationDay(PREDICTOR_SUB_DELTA_DAY_DEFAULT)
+  ,mSubresourceDegradationWeek(PREDICTOR_SUB_DELTA_WEEK_DEFAULT)
+  ,mSubresourceDegradationMonth(PREDICTOR_SUB_DELTA_MONTH_DEFAULT)
+  ,mSubresourceDegradationYear(PREDICTOR_SUB_DELTA_YEAR_DEFAULT)
+  ,mSubresourceDegradationMax(PREDICTOR_SUB_DELTA_MAX_DEFAULT)
+  ,mPrefetchRollingLoadCount(PREFETCH_ROLLING_LOAD_DEFAULT)
+  ,mPrefetchMinConfidence(PREFETCH_MIN_DEFAULT)
+  ,mPreconnectMinConfidence(PRECONNECT_MIN_DEFAULT)
+  ,mPreresolveMinConfidence(PRERESOLVE_MIN_DEFAULT)
+  ,mRedirectLikelyConfidence(REDIRECT_LIKELY_DEFAULT)
+  ,mPrefetchForceValidFor(PREFETCH_FORCE_VALID_DEFAULT)
+  ,mMaxResourcesPerEntry(PREDICTOR_MAX_RESOURCES_DEFAULT)
+  ,mStartupCount(1)
+  ,mMaxURILength(PREDICTOR_MAX_URI_LENGTH_DEFAULT)
+  ,mDoingTests(false)
+{
+  MOZ_ASSERT(!sSelf, "multiple Predictor instances!");
+  sSelf = this;
+}
+
+Predictor::~Predictor()
+{
+  if (mInitialized)
+    Shutdown();
+
+  sSelf = nullptr;
+}
+
+// Predictor::nsIObserver
+
+nsresult
+Predictor::InstallObserver()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Installing observer off main thread");
+
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIObserverService> obs =
+    mozilla::services::GetObserverService();
+  if (!obs) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  rv = obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  Preferences::AddBoolVarCache(&mEnabled, PREDICTOR_ENABLED_PREF, true);
+  Preferences::AddBoolVarCache(&mEnableHoverOnSSL,
+                               PREDICTOR_SSL_HOVER_PREF, false);
+  Preferences::AddBoolVarCache(&mEnablePrefetch, PREDICTOR_PREFETCH_PREF, true);
+  Preferences::AddIntVarCache(&mPageDegradationDay,
+                              PREDICTOR_PAGE_DELTA_DAY_PREF,
+                              PREDICTOR_PAGE_DELTA_DAY_DEFAULT);
+  Preferences::AddIntVarCache(&mPageDegradationWeek,
+                              PREDICTOR_PAGE_DELTA_WEEK_PREF,
+                              PREDICTOR_PAGE_DELTA_WEEK_DEFAULT);
+  Preferences::AddIntVarCache(&mPageDegradationMonth,
+                              PREDICTOR_PAGE_DELTA_MONTH_PREF,
+                              PREDICTOR_PAGE_DELTA_MONTH_DEFAULT);
+  Preferences::AddIntVarCache(&mPageDegradationYear,
+                              PREDICTOR_PAGE_DELTA_YEAR_PREF,
+                              PREDICTOR_PAGE_DELTA_YEAR_DEFAULT);
+  Preferences::AddIntVarCache(&mPageDegradationMax,
+                              PREDICTOR_PAGE_DELTA_MAX_PREF,
+                              PREDICTOR_PAGE_DELTA_MAX_DEFAULT);
+
+  Preferences::AddIntVarCache(&mSubresourceDegradationDay,
+                              PREDICTOR_SUB_DELTA_DAY_PREF,
+                              PREDICTOR_SUB_DELTA_DAY_DEFAULT);
+  Preferences::AddIntVarCache(&mSubresourceDegradationWeek,
+                              PREDICTOR_SUB_DELTA_WEEK_PREF,
+                              PREDICTOR_SUB_DELTA_WEEK_DEFAULT);
+  Preferences::AddIntVarCache(&mSubresourceDegradationMonth,
+                              PREDICTOR_SUB_DELTA_MONTH_PREF,
+                              PREDICTOR_SUB_DELTA_MONTH_DEFAULT);
+  Preferences::AddIntVarCache(&mSubresourceDegradationYear,
+                              PREDICTOR_SUB_DELTA_YEAR_PREF,
+                              PREDICTOR_SUB_DELTA_YEAR_DEFAULT);
+  Preferences::AddIntVarCache(&mSubresourceDegradationMax,
+                              PREDICTOR_SUB_DELTA_MAX_PREF,
+                              PREDICTOR_SUB_DELTA_MAX_DEFAULT);
+
+  Preferences::AddIntVarCache(&mPrefetchRollingLoadCount,
+                              PREDICTOR_PREFETCH_ROLLING_LOAD_PREF,
+                              PREFETCH_ROLLING_LOAD_DEFAULT);
+  Preferences::AddIntVarCache(&mPrefetchMinConfidence,
+                              PREDICTOR_PREFETCH_MIN_PREF,
+                              PREFETCH_MIN_DEFAULT);
+  Preferences::AddIntVarCache(&mPreconnectMinConfidence,
+                              PREDICTOR_PRECONNECT_MIN_PREF,
+                              PRECONNECT_MIN_DEFAULT);
+  Preferences::AddIntVarCache(&mPreresolveMinConfidence,
+                              PREDICTOR_PRERESOLVE_MIN_PREF,
+                              PRERESOLVE_MIN_DEFAULT);
+  Preferences::AddIntVarCache(&mRedirectLikelyConfidence,
+                              PREDICTOR_REDIRECT_LIKELY_PREF,
+                              REDIRECT_LIKELY_DEFAULT);
+
+  Preferences::AddIntVarCache(&mPrefetchForceValidFor,
+                              PREDICTOR_PREFETCH_FORCE_VALID_PREF,
+                              PREFETCH_FORCE_VALID_DEFAULT);
+
+  Preferences::AddIntVarCache(&mMaxResourcesPerEntry,
+                              PREDICTOR_MAX_RESOURCES_PREF,
+                              PREDICTOR_MAX_RESOURCES_DEFAULT);
+
+  Preferences::AddBoolVarCache(&mCleanedUp, PREDICTOR_CLEANED_UP_PREF, false);
+
+  Preferences::AddUintVarCache(&mMaxURILength, PREDICTOR_MAX_URI_LENGTH_PREF,
+                               PREDICTOR_MAX_URI_LENGTH_DEFAULT);
+
+  Preferences::AddBoolVarCache(&mDoingTests, PREDICTOR_DOING_TESTS_PREF, false);
+
+  if (!mCleanedUp) {
+    mCleanupTimer = do_CreateInstance("@mozilla.org/timer;1");
+    mCleanupTimer->Init(this, 60 * 1000, nsITimer::TYPE_ONE_SHOT);
+  }
+
+  return rv;
+}
+
+void
+Predictor::RemoveObserver()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Removing observer off main thread");
+
+  nsCOMPtr<nsIObserverService> obs =
+    mozilla::services::GetObserverService();
+  if (obs) {
+    obs->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
+  }
+
+  if (mCleanupTimer) {
+    mCleanupTimer->Cancel();
+    mCleanupTimer = nullptr;
+  }
+}
+
+NS_IMETHODIMP
+Predictor::Observe(nsISupports *subject, const char *topic,
+                   const char16_t *data_unicode)
+{
+  nsresult rv = NS_OK;
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Predictor observing something off main thread!");
+
+  if (!strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, topic)) {
+    Shutdown();
+  } else if (!strcmp("timer-callback", topic)) {
+    MaybeCleanupOldDBFiles();
+    mCleanupTimer = nullptr;
+  }
+
+  return rv;
+}
+
+// Predictor::nsISpeculativeConnectionOverrider
+
+NS_IMETHODIMP
+Predictor::GetIgnoreIdle(bool *ignoreIdle)
+{
+  *ignoreIdle = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::GetParallelSpeculativeConnectLimit(
+    uint32_t *parallelSpeculativeConnectLimit)
+{
+  *parallelSpeculativeConnectLimit = 6;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::GetIsFromPredictor(bool *isFromPredictor)
+{
+  *isFromPredictor = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::GetAllow1918(bool *allow1918)
+{
+  *allow1918 = false;
+  return NS_OK;
+}
+
+// Predictor::nsIInterfaceRequestor
+
+NS_IMETHODIMP
+Predictor::GetInterface(const nsIID &iid, void **result)
+{
+  return QueryInterface(iid, result);
+}
+
+// Predictor::nsICacheEntryMetaDataVisitor
+
+#define SEEN_META_DATA "predictor::seen"
+#define RESOURCE_META_DATA "predictor::resource-count"
+#define META_DATA_PREFIX "predictor::"
+
+static bool
+IsURIMetadataElement(const char *key)
+{
+  return StringBeginsWith(nsDependentCString(key),
+                          NS_LITERAL_CSTRING(META_DATA_PREFIX)) &&
+         !NS_LITERAL_CSTRING(SEEN_META_DATA).Equals(key) &&
+         !NS_LITERAL_CSTRING(RESOURCE_META_DATA).Equals(key);
+}
+
+nsresult
+Predictor::OnMetaDataElement(const char *asciiKey, const char *asciiValue)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsURIMetadataElement(asciiKey)) {
+    // This isn't a bit of metadata we care about
+    return NS_OK;
+  }
+
+  nsCString key, value;
+  key.AssignASCII(asciiKey);
+  value.AssignASCII(asciiValue);
+  mKeysToOperateOn.AppendElement(key);
+  mValuesToOperateOn.AppendElement(value);
+
+  return NS_OK;
+}
+
+// Predictor::nsINetworkPredictor
+
+nsresult
+Predictor::Init()
+{
+  MOZ_DIAGNOSTIC_ASSERT(!IsNeckoChild());
+
+  if (!NS_IsMainThread()) {
+    MOZ_ASSERT(false, "Predictor::Init called off the main thread!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsresult rv = NS_OK;
+
+  rv = InstallObserver();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mLastStartupTime = mStartupTime = NOW_IN_SECONDS();
+
+  if (!mDNSListener) {
+    mDNSListener = new DNSListener();
+  }
+
+  nsCOMPtr<nsICacheStorageService> cacheStorageService =
+    do_GetService("@mozilla.org/netwerk/cache-storage-service;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<LoadContextInfo> lci =
+    new LoadContextInfo(false, NeckoOriginAttributes());
+
+  rv = cacheStorageService->DiskCacheStorage(lci, false,
+                                             getter_AddRefs(mCacheDiskStorage));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mIOService = do_GetService("@mozilla.org/network/io-service;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = NS_NewURI(getter_AddRefs(mStartupURI),
+                 "predictor://startup", nullptr, mIOService);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mSpeculativeService = do_QueryInterface(mIOService, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mDnsService = do_GetService("@mozilla.org/network/dns-service;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mInitialized = true;
+
+  return rv;
+}
+
+namespace {
+class PredictorThreadShutdownRunner : public Runnable
+{
+public:
+  PredictorThreadShutdownRunner(nsIThread *ioThread, bool success)
+    :mIOThread(ioThread)
+    ,mSuccess(success)
+  { }
+  ~PredictorThreadShutdownRunner() { }
+
+  NS_IMETHOD Run() override
+  {
+    MOZ_ASSERT(NS_IsMainThread(), "Shutting down io thread off main thread!");
+    if (mSuccess) {
+      // This means the cleanup happened. Mark so we don't try in the
+      // future.
+      Preferences::SetBool(PREDICTOR_CLEANED_UP_PREF, true);
+    }
+    return mIOThread->AsyncShutdown();
+  }
+
+private:
+  nsCOMPtr<nsIThread> mIOThread;
+  bool mSuccess;
+};
+
+class PredictorOldCleanupRunner : public Runnable
+{
+public:
+  PredictorOldCleanupRunner(nsIThread *ioThread, nsIFile *dbFile)
+    :mIOThread(ioThread)
+    ,mDBFile(dbFile)
+  { }
+
+  ~PredictorOldCleanupRunner() { }
+
+  NS_IMETHOD Run() override
+  {
+    MOZ_ASSERT(!NS_IsMainThread(), "Cleaning up old files on main thread!");
+    nsresult rv = CheckForAndDeleteOldDBFiles();
+    RefPtr<PredictorThreadShutdownRunner> runner =
+      new PredictorThreadShutdownRunner(mIOThread, NS_SUCCEEDED(rv));
+    NS_DispatchToMainThread(runner);
+    return NS_OK;
+  }
+
+private:
+  nsresult CheckForAndDeleteOldDBFiles()
+  {
+    nsCOMPtr<nsIFile> oldDBFile;
+    nsresult rv = mDBFile->GetParent(getter_AddRefs(oldDBFile));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = oldDBFile->AppendNative(NS_LITERAL_CSTRING("seer.sqlite"));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    bool fileExists = false;
+    rv = oldDBFile->Exists(&fileExists);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (fileExists) {
+      rv = oldDBFile->Remove(false);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    fileExists = false;
+    rv = mDBFile->Exists(&fileExists);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (fileExists) {
+      rv = mDBFile->Remove(false);
+    }
+
+    return rv;
+  }
+
+  nsCOMPtr<nsIThread> mIOThread;
+  nsCOMPtr<nsIFile> mDBFile;
+};
+
+} // namespace
+
+void
+Predictor::MaybeCleanupOldDBFiles()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!mEnabled || mCleanedUp) {
+    return;
+  }
+
+  mCleanedUp = true;
+
+  // This is used for cleaning up junk left over from the old backend
+  // built on top of sqlite, if necessary.
+  nsCOMPtr<nsIFile> dbFile;
+  nsresult rv = NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                                       getter_AddRefs(dbFile));
+  RETURN_IF_FAILED(rv);
+  rv = dbFile->AppendNative(NS_LITERAL_CSTRING("netpredictions.sqlite"));
+  RETURN_IF_FAILED(rv);
+
+  nsCOMPtr<nsIThread> ioThread;
+  rv = NS_NewNamedThread("NetPredictClean", getter_AddRefs(ioThread));
+  RETURN_IF_FAILED(rv);
+
+  RefPtr<PredictorOldCleanupRunner> runner =
+    new PredictorOldCleanupRunner(ioThread, dbFile);
+  ioThread->Dispatch(runner, NS_DISPATCH_NORMAL);
+}
+
+void
+Predictor::Shutdown()
+{
+  if (!NS_IsMainThread()) {
+    MOZ_ASSERT(false, "Predictor::Shutdown called off the main thread!");
+    return;
+  }
+
+  RemoveObserver();
+
+  mInitialized = false;
+}
+
+nsresult
+Predictor::Create(nsISupports *aOuter, const nsIID& aIID,
+                  void **aResult)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsresult rv;
+
+  if (aOuter != nullptr) {
+    return NS_ERROR_NO_AGGREGATION;
+  }
+
+  RefPtr<Predictor> svc = new Predictor();
+  if (IsNeckoChild()) {
+    // Child threads only need to be call into the public interface methods
+    // so we don't bother with initialization
+    return svc->QueryInterface(aIID, aResult);
+  }
+
+  rv = svc->Init();
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("Failed to initialize predictor, predictor will be a noop"));
+  }
+
+  // We treat init failure the same as the service being disabled, since this
+  // is all an optimization anyway. No need to freak people out. That's why we
+  // gladly continue on QI'ing here.
+  rv = svc->QueryInterface(aIID, aResult);
+
+  return rv;
+}
+
+// Called from the main thread to initiate predictive actions
+NS_IMETHODIMP
+Predictor::Predict(nsIURI *targetURI, nsIURI *sourceURI,
+                   PredictorPredictReason reason, nsILoadContext *loadContext,
+                   nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Predictor interface methods must be called on the main thread");
+
+  PREDICTOR_LOG(("Predictor::Predict"));
+
+  if (IsNeckoChild()) {
+    MOZ_DIAGNOSTIC_ASSERT(gNeckoChild);
+
+    PREDICTOR_LOG(("    called on child process"));
+
+    ipc::OptionalURIParams serTargetURI, serSourceURI;
+    SerializeURI(targetURI, serTargetURI);
+    SerializeURI(sourceURI, serSourceURI);
+
+    IPC::SerializedLoadContext serLoadContext;
+    serLoadContext.Init(loadContext);
+
+    // If two different threads are predicting concurently, this will be
+    // overwritten. Thankfully, we only use this in tests, which will
+    // overwrite mVerifier perhaps multiple times for each individual test;
+    // however, within each test, the multiple predict calls should have the
+    // same verifier.
+    if (verifier) {
+      PREDICTOR_LOG(("    was given a verifier"));
+      mChildVerifier = verifier;
+    }
+    PREDICTOR_LOG(("    forwarding to parent process"));
+    gNeckoChild->SendPredPredict(serTargetURI, serSourceURI,
+                                 reason, serLoadContext, verifier);
+    return NS_OK;
+  }
+
+  PREDICTOR_LOG(("    called on parent process"));
+
+  if (!mInitialized) {
+    PREDICTOR_LOG(("    not initialized"));
+    return NS_OK;
+  }
+
+  if (!mEnabled) {
+    PREDICTOR_LOG(("    not enabled"));
+    return NS_OK;
+  }
+
+  if (loadContext && loadContext->UsePrivateBrowsing()) {
+    // Don't want to do anything in PB mode
+    PREDICTOR_LOG(("    in PB mode"));
+    return NS_OK;
+  }
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    // Nothing we can do for non-HTTP[S] schemes
+    PREDICTOR_LOG(("    got non-http[s] URI"));
+    return NS_OK;
+  }
+
+  // Ensure we've been given the appropriate arguments for the kind of
+  // prediction we're being asked to do
+  nsCOMPtr<nsIURI> uriKey = targetURI;
+  nsCOMPtr<nsIURI> originKey;
+  switch (reason) {
+    case nsINetworkPredictor::PREDICT_LINK:
+      if (!targetURI || !sourceURI) {
+        PREDICTOR_LOG(("    link invalid URI state"));
+        return NS_ERROR_INVALID_ARG;
+      }
+      // Link hover is a special case where we can predict without hitting the
+      // db, so let's go ahead and fire off that prediction here.
+      PredictForLink(targetURI, sourceURI, verifier);
+      return NS_OK;
+    case nsINetworkPredictor::PREDICT_LOAD:
+      if (!targetURI || sourceURI) {
+        PREDICTOR_LOG(("    load invalid URI state"));
+        return NS_ERROR_INVALID_ARG;
+      }
+      break;
+    case nsINetworkPredictor::PREDICT_STARTUP:
+      if (targetURI || sourceURI) {
+        PREDICTOR_LOG(("    startup invalid URI state"));
+        return NS_ERROR_INVALID_ARG;
+      }
+      uriKey = mStartupURI;
+      originKey = mStartupURI;
+      break;
+    default:
+      PREDICTOR_LOG(("    invalid reason"));
+      return NS_ERROR_INVALID_ARG;
+  }
+
+  Predictor::Reason argReason;
+  argReason.mPredict = reason;
+
+  // First we open the regular cache entry, to ensure we don't gum up the works
+  // waiting on the less-important predictor-only cache entry
+  RefPtr<Predictor::Action> uriAction =
+    new Predictor::Action(Predictor::Action::IS_FULL_URI,
+                          Predictor::Action::DO_PREDICT, argReason, targetURI,
+                          nullptr, verifier, this);
+  nsAutoCString uriKeyStr;
+  uriKey->GetAsciiSpec(uriKeyStr);
+  PREDICTOR_LOG(("    Predict uri=%s reason=%d action=%p", uriKeyStr.get(),
+                 reason, uriAction.get()));
+  uint32_t openFlags = nsICacheStorage::OPEN_READONLY |
+                       nsICacheStorage::OPEN_SECRETLY |
+                       nsICacheStorage::OPEN_PRIORITY |
+                       nsICacheStorage::CHECK_MULTITHREADED;
+  mCacheDiskStorage->AsyncOpenURI(uriKey, EmptyCString(), openFlags, uriAction);
+
+  // Now we do the origin-only (and therefore predictor-only) entry
+  nsCOMPtr<nsIURI> targetOrigin;
+  nsresult rv = ExtractOrigin(uriKey, getter_AddRefs(targetOrigin), mIOService);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!originKey) {
+    originKey = targetOrigin;
+  }
+
+  RefPtr<Predictor::Action> originAction =
+    new Predictor::Action(Predictor::Action::IS_ORIGIN,
+                          Predictor::Action::DO_PREDICT, argReason,
+                          targetOrigin, nullptr, verifier, this);
+  nsAutoCString originKeyStr;
+  originKey->GetAsciiSpec(originKeyStr);
+  PREDICTOR_LOG(("    Predict origin=%s reason=%d action=%p", originKeyStr.get(),
+                 reason, originAction.get()));
+  openFlags = nsICacheStorage::OPEN_READONLY |
+              nsICacheStorage::OPEN_SECRETLY |
+              nsICacheStorage::CHECK_MULTITHREADED;
+  mCacheDiskStorage->AsyncOpenURI(originKey,
+                                  NS_LITERAL_CSTRING(PREDICTOR_ORIGIN_EXTENSION),
+                                  openFlags, originAction);
+
+  PREDICTOR_LOG(("    predict returning"));
+  return NS_OK;
+}
+
+bool
+Predictor::PredictInternal(PredictorPredictReason reason, nsICacheEntry *entry,
+                           bool isNew, bool fullUri, nsIURI *targetURI,
+                           nsINetworkPredictorVerifier *verifier,
+                           uint8_t stackCount)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::PredictInternal"));
+  bool rv = false;
+
+  if (reason == nsINetworkPredictor::PREDICT_LOAD) {
+    MaybeLearnForStartup(targetURI, fullUri);
+  }
+
+  if (isNew) {
+    // nothing else we can do here
+    PREDICTOR_LOG(("    new entry"));
+    return rv;
+  }
+
+  switch (reason) {
+    case nsINetworkPredictor::PREDICT_LOAD:
+      rv = PredictForPageload(entry, targetURI, stackCount, fullUri, verifier);
+      break;
+    case nsINetworkPredictor::PREDICT_STARTUP:
+      rv = PredictForStartup(entry, fullUri, verifier);
+      break;
+    default:
+      PREDICTOR_LOG(("    invalid reason"));
+      MOZ_ASSERT(false, "Got unexpected value for prediction reason");
+  }
+
+  return rv;
+}
+
+void
+Predictor::PredictForLink(nsIURI *targetURI, nsIURI *sourceURI,
+                          nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::PredictForLink"));
+  if (!mSpeculativeService) {
+    PREDICTOR_LOG(("    missing speculative service"));
+    return;
+  }
+
+  if (!mEnableHoverOnSSL) {
+    bool isSSL = false;
+    sourceURI->SchemeIs("https", &isSSL);
+    if (isSSL) {
+      // We don't want to predict from an HTTPS page, to avoid info leakage
+      PREDICTOR_LOG(("    Not predicting for link hover - on an SSL page"));
+      return;
+    }
+  }
+
+  mSpeculativeService->SpeculativeConnect2(targetURI, nullptr, nullptr);
+  if (verifier) {
+    PREDICTOR_LOG(("    sending verification"));
+    verifier->OnPredictPreconnect(targetURI);
+  }
+}
+
+// This is the driver for prediction based on a new pageload.
+static const uint8_t MAX_PAGELOAD_DEPTH = 10;
+bool
+Predictor::PredictForPageload(nsICacheEntry *entry, nsIURI *targetURI,
+                              uint8_t stackCount, bool fullUri,
+                              nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::PredictForPageload"));
+
+  if (stackCount > MAX_PAGELOAD_DEPTH) {
+    PREDICTOR_LOG(("    exceeded recursion depth!"));
+    return false;
+  }
+
+  uint32_t lastLoad;
+  nsresult rv = entry->GetLastFetched(&lastLoad);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  int32_t globalDegradation = CalculateGlobalDegradation(lastLoad);
+  PREDICTOR_LOG(("    globalDegradation = %d", globalDegradation));
+
+  int32_t loadCount;
+  rv = entry->GetFetchCount(&loadCount);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsCOMPtr<nsIURI> redirectURI;
+  if (WouldRedirect(entry, loadCount, lastLoad, globalDegradation,
+                    getter_AddRefs(redirectURI))) {
+    mPreconnects.AppendElement(redirectURI);
+    Predictor::Reason reason;
+    reason.mPredict = nsINetworkPredictor::PREDICT_LOAD;
+    RefPtr<Predictor::Action> redirectAction =
+      new Predictor::Action(Predictor::Action::IS_FULL_URI,
+                            Predictor::Action::DO_PREDICT, reason, redirectURI,
+                            nullptr, verifier, this, stackCount + 1);
+    nsAutoCString redirectUriString;
+    redirectURI->GetAsciiSpec(redirectUriString);
+    PREDICTOR_LOG(("    Predict redirect uri=%s action=%p", redirectUriString.get(),
+                   redirectAction.get()));
+    uint32_t openFlags = nsICacheStorage::OPEN_READONLY |
+                         nsICacheStorage::OPEN_SECRETLY |
+                         nsICacheStorage::OPEN_PRIORITY |
+                         nsICacheStorage::CHECK_MULTITHREADED;
+    mCacheDiskStorage->AsyncOpenURI(redirectURI, EmptyCString(), openFlags,
+                                    redirectAction);
+    return RunPredictions(nullptr, verifier);
+  }
+
+  CalculatePredictions(entry, targetURI, lastLoad, loadCount, globalDegradation, fullUri);
+
+  return RunPredictions(targetURI, verifier);
+}
+
+// This is the driver for predicting at browser startup time based on pages that
+// have previously been loaded close to startup.
+bool
+Predictor::PredictForStartup(nsICacheEntry *entry, bool fullUri,
+                             nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::PredictForStartup"));
+  int32_t globalDegradation = CalculateGlobalDegradation(mLastStartupTime);
+  CalculatePredictions(entry, nullptr, mLastStartupTime, mStartupCount,
+                       globalDegradation, fullUri);
+  return RunPredictions(nullptr, verifier);
+}
+
+// This calculates how much to degrade our confidence in our data based on
+// the last time this top-level resource was loaded. This "global degradation"
+// applies to *all* subresources we have associated with the top-level
+// resource. This will be in addition to any reduction in confidence we have
+// associated with a particular subresource.
+int32_t
+Predictor::CalculateGlobalDegradation(uint32_t lastLoad)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  int32_t globalDegradation;
+  uint32_t delta = NOW_IN_SECONDS() - lastLoad;
+  if (delta < ONE_DAY) {
+    globalDegradation = mPageDegradationDay;
+  } else if (delta < ONE_WEEK) {
+    globalDegradation = mPageDegradationWeek;
+  } else if (delta < ONE_MONTH) {
+    globalDegradation = mPageDegradationMonth;
+  } else if (delta < ONE_YEAR) {
+    globalDegradation = mPageDegradationYear;
+  } else {
+    globalDegradation = mPageDegradationMax;
+  }
+
+  Telemetry::Accumulate(Telemetry::PREDICTOR_GLOBAL_DEGRADATION,
+                        globalDegradation);
+  return globalDegradation;
+}
+
+// This calculates our overall confidence that a particular subresource will be
+// loaded as part of a top-level load.
+// @param hitCount - the number of times we have loaded this subresource as part
+//                   of this top-level load
+// @param hitsPossible - the number of times we have performed this top-level
+//                       load
+// @param lastHit - the timestamp of the last time we loaded this subresource as
+//                  part of this top-level load
+// @param lastPossible - the timestamp of the last time we performed this
+//                       top-level load
+// @param globalDegradation - the degradation for this top-level load as
+//                            determined by CalculateGlobalDegradation
+int32_t
+Predictor::CalculateConfidence(uint32_t hitCount, uint32_t hitsPossible,
+                               uint32_t lastHit, uint32_t lastPossible,
+                               int32_t globalDegradation)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_PREDICTIONS_CALCULATED> predictionsCalculated;
+  ++predictionsCalculated;
+
+  if (!hitsPossible) {
+    return 0;
+  }
+
+  int32_t baseConfidence = (hitCount * 100) / hitsPossible;
+  int32_t maxConfidence = 100;
+  int32_t confidenceDegradation = 0;
+
+  if (lastHit < lastPossible) {
+    // We didn't load this subresource the last time this top-level load was
+    // performed, so let's not bother preconnecting (at the very least).
+    maxConfidence = mPreconnectMinConfidence - 1;
+
+    // Now calculate how much we want to degrade our confidence based on how
+    // long it's been between the last time we did this top-level load and the
+    // last time this top-level load included this subresource.
+    PRTime delta = lastPossible - lastHit;
+    if (delta == 0) {
+      confidenceDegradation = 0;
+    } else if (delta < ONE_DAY) {
+      confidenceDegradation = mSubresourceDegradationDay;
+    } else if (delta < ONE_WEEK) {
+      confidenceDegradation = mSubresourceDegradationWeek;
+    } else if (delta < ONE_MONTH) {
+      confidenceDegradation = mSubresourceDegradationMonth;
+    } else if (delta < ONE_YEAR) {
+      confidenceDegradation = mSubresourceDegradationYear;
+    } else {
+      confidenceDegradation = mSubresourceDegradationMax;
+      maxConfidence = 0;
+    }
+  }
+
+  // Calculate our confidence and clamp it to between 0 and maxConfidence
+  // (<= 100)
+  int32_t confidence = baseConfidence - confidenceDegradation - globalDegradation;
+  confidence = std::max(confidence, 0);
+  confidence = std::min(confidence, maxConfidence);
+
+  Telemetry::Accumulate(Telemetry::PREDICTOR_BASE_CONFIDENCE, baseConfidence);
+  Telemetry::Accumulate(Telemetry::PREDICTOR_SUBRESOURCE_DEGRADATION,
+                        confidenceDegradation);
+  Telemetry::Accumulate(Telemetry::PREDICTOR_CONFIDENCE, confidence);
+  return confidence;
+}
+
+static void
+MakeMetadataEntry(const uint32_t hitCount, const uint32_t lastHit,
+                  const uint32_t flags, nsCString &newValue)
+{
+  newValue.Truncate();
+  newValue.AppendInt(METADATA_VERSION);
+  newValue.Append(',');
+  newValue.AppendInt(hitCount);
+  newValue.Append(',');
+  newValue.AppendInt(lastHit);
+  newValue.Append(',');
+  newValue.AppendInt(flags);
+}
+
+// On every page load, the rolling window gets shifted by one bit, leaving the
+// lowest bit at 0, to indicate that the subresource in question has not been
+// seen on the most recent page load. If, at some point later during the page load,
+// the subresource is seen again, we will then set the lowest bit to 1. This is
+// how we keep track of how many of the last n pageloads (for n <= 20) a particular
+// subresource has been seen.
+// The rolling window is kept in the upper 20 bits of the flags element of the
+// metadata. This saves 12 bits for regular old flags.
+void
+Predictor::UpdateRollingLoadCount(nsICacheEntry *entry, const uint32_t flags,
+                                  const char *key, const uint32_t hitCount,
+                                  const uint32_t lastHit)
+{
+  // Extract just the rolling load count from the flags, shift it to clear the
+  // lowest bit, and put the new value with the existing flags.
+  uint32_t rollingLoadCount = flags & ~kFlagsMask;
+  rollingLoadCount <<= 1;
+  uint32_t newFlags = (flags & kFlagsMask) | rollingLoadCount;
+
+  // Finally, update the metadata on the cache entry.
+  nsAutoCString newValue;
+  MakeMetadataEntry(hitCount, lastHit, newFlags, newValue);
+  entry->SetMetaDataElement(key, newValue.BeginReading());
+}
+
+void
+Predictor::SanitizePrefs()
+{
+  if (mPrefetchRollingLoadCount < 0) {
+    mPrefetchRollingLoadCount = 0;
+  } else if (mPrefetchRollingLoadCount > kMaxPrefetchRollingLoadCount) {
+    mPrefetchRollingLoadCount = kMaxPrefetchRollingLoadCount;
+  }
+}
+
+void
+Predictor::CalculatePredictions(nsICacheEntry *entry, nsIURI *referrer,
+                                uint32_t lastLoad, uint32_t loadCount,
+                                int32_t globalDegradation, bool fullUri)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  SanitizePrefs();
+
+  // Since the visitor gets called under a cache lock, all we do there is get
+  // copies of the keys/values we care about, and then do the real work here
+  entry->VisitMetaData(this);
+  nsTArray<nsCString> keysToOperateOn, valuesToOperateOn;
+  keysToOperateOn.SwapElements(mKeysToOperateOn);
+  valuesToOperateOn.SwapElements(mValuesToOperateOn);
+
+  MOZ_ASSERT(keysToOperateOn.Length() == valuesToOperateOn.Length());
+  for (size_t i = 0; i < keysToOperateOn.Length(); ++i) {
+    const char *key = keysToOperateOn[i].BeginReading();
+    const char *value = valuesToOperateOn[i].BeginReading();
+
+    nsCOMPtr<nsIURI> uri;
+    uint32_t hitCount, lastHit, flags;
+    if (!ParseMetaDataEntry(key, value, getter_AddRefs(uri), hitCount, lastHit, flags)) {
+      // This failed, get rid of it so we don't waste space
+      entry->SetMetaDataElement(key, nullptr);
+      continue;
+    }
+
+    int32_t confidence = CalculateConfidence(hitCount, loadCount, lastHit,
+                                             lastLoad, globalDegradation);
+    if (fullUri) {
+      UpdateRollingLoadCount(entry, flags, key, hitCount, lastHit);
+    }
+    PREDICTOR_LOG(("CalculatePredictions key=%s value=%s confidence=%d", key, value, confidence));
+    if (!fullUri) {
+      // Not full URI - don't prefetch! No sense in it!
+      PREDICTOR_LOG(("    forcing non-cacheability - not full URI"));
+      flags &= ~FLAG_PREFETCHABLE;
+    } else if (!referrer) {
+      // No referrer means we can't prefetch, so pretend it's non-cacheable,
+      // no matter what.
+      PREDICTOR_LOG(("    forcing non-cacheability - no referrer"));
+      flags &= ~FLAG_PREFETCHABLE;
+    } else {
+      uint32_t expectedRollingLoadCount = (1 << mPrefetchRollingLoadCount) - 1;
+      expectedRollingLoadCount <<= kRollingLoadOffset;
+      if ((flags & expectedRollingLoadCount) != expectedRollingLoadCount) {
+        PREDICTOR_LOG(("    forcing non-cacheability - missed a load"));
+        flags &= ~FLAG_PREFETCHABLE;
+      }
+    }
+
+    PREDICTOR_LOG(("    setting up prediction"));
+    SetupPrediction(confidence, flags, uri);
+  }
+}
+
+// (Maybe) adds a predictive action to the prediction runner, based on our
+// calculated confidence for the subresource in question.
+void
+Predictor::SetupPrediction(int32_t confidence, uint32_t flags, nsIURI *uri)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsAutoCString uriStr;
+  uri->GetAsciiSpec(uriStr);
+  PREDICTOR_LOG(("SetupPrediction mEnablePrefetch=%d mPrefetchMinConfidence=%d "
+                 "mPreconnectMinConfidence=%d mPreresolveMinConfidence=%d "
+                 "flags=%d confidence=%d uri=%s", mEnablePrefetch,
+                 mPrefetchMinConfidence, mPreconnectMinConfidence,
+                 mPreresolveMinConfidence, flags, confidence, uriStr.get()));
+  if (mEnablePrefetch && (flags & FLAG_PREFETCHABLE) &&
+      (mPrefetchRollingLoadCount || (confidence >= mPrefetchMinConfidence))) {
+    mPrefetches.AppendElement(uri);
+  } else if (confidence >= mPreconnectMinConfidence) {
+    mPreconnects.AppendElement(uri);
+  } else if (confidence >= mPreresolveMinConfidence) {
+    mPreresolves.AppendElement(uri);
+  }
+}
+
+nsresult
+Predictor::Prefetch(nsIURI *uri, nsIURI *referrer,
+                    nsINetworkPredictorVerifier *verifier)
+{
+  nsAutoCString strUri, strReferrer;
+  uri->GetAsciiSpec(strUri);
+  referrer->GetAsciiSpec(strReferrer);
+  PREDICTOR_LOG(("Predictor::Prefetch uri=%s referrer=%s verifier=%p",
+                 strUri.get(), strReferrer.get(), verifier));
+  nsCOMPtr<nsIChannel> channel;
+  nsresult rv = NS_NewChannel(getter_AddRefs(channel), uri,
+                              nsContentUtils::GetSystemPrincipal(),
+                              nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_IS_NULL,
+                              nsIContentPolicy::TYPE_OTHER,
+                              nullptr, /* aLoadGroup */
+                              nullptr, /* aCallbacks */
+                              nsIRequest::LOAD_BACKGROUND);
+
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("    NS_NewChannel failed rv=0x%X", rv));
+    return rv;
+  }
+
+  nsCOMPtr<nsIHttpChannel> httpChannel;
+  httpChannel = do_QueryInterface(channel);
+  if (!httpChannel) {
+    PREDICTOR_LOG(("    Could not get HTTP Channel from new channel!"));
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  httpChannel->SetReferrer(referrer);
+  // XXX - set a header here to indicate this is a prefetch?
+
+  nsCOMPtr<nsIStreamListener> listener = new PrefetchListener(verifier, uri,
+                                                              this);
+  PREDICTOR_LOG(("    calling AsyncOpen2 listener=%p channel=%p", listener.get(),
+                 channel.get()));
+  rv = channel->AsyncOpen2(listener);
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("    AsyncOpen2 failed rv=0x%X", rv));
+  }
+
+  return rv;
+}
+
+// Runs predictions that have been set up.
+bool
+Predictor::RunPredictions(nsIURI *referrer, nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Running prediction off main thread");
+
+  PREDICTOR_LOG(("Predictor::RunPredictions"));
+
+  bool predicted = false;
+  uint32_t len, i;
+
+  nsTArray<nsCOMPtr<nsIURI>> prefetches, preconnects, preresolves;
+  prefetches.SwapElements(mPrefetches);
+  preconnects.SwapElements(mPreconnects);
+  preresolves.SwapElements(mPreresolves);
+
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_TOTAL_PREDICTIONS> totalPredictions;
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_TOTAL_PREFETCHES> totalPrefetches;
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_TOTAL_PRECONNECTS> totalPreconnects;
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_TOTAL_PRERESOLVES> totalPreresolves;
+
+  len = prefetches.Length();
+  for (i = 0; i < len; ++i) {
+    PREDICTOR_LOG(("    doing prefetch"));
+    nsCOMPtr<nsIURI> uri = prefetches[i];
+    if (NS_SUCCEEDED(Prefetch(uri, referrer, verifier))) {
+      ++totalPredictions;
+      ++totalPrefetches;
+      predicted = true;
+    }
+  }
+
+  len = preconnects.Length();
+  for (i = 0; i < len; ++i) {
+    PREDICTOR_LOG(("    doing preconnect"));
+    nsCOMPtr<nsIURI> uri = preconnects[i];
+    ++totalPredictions;
+    ++totalPreconnects;
+    mSpeculativeService->SpeculativeConnect2(uri, nullptr, this);
+    predicted = true;
+    if (verifier) {
+      PREDICTOR_LOG(("    sending preconnect verification"));
+      verifier->OnPredictPreconnect(uri);
+    }
+  }
+
+  len = preresolves.Length();
+  nsCOMPtr<nsIThread> mainThread = do_GetMainThread();
+  for (i = 0; i < len; ++i) {
+    nsCOMPtr<nsIURI> uri = preresolves[i];
+    ++totalPredictions;
+    ++totalPreresolves;
+    nsAutoCString hostname;
+    uri->GetAsciiHost(hostname);
+    PREDICTOR_LOG(("    doing preresolve %s", hostname.get()));
+    nsCOMPtr<nsICancelable> tmpCancelable;
+    mDnsService->AsyncResolve(hostname,
+                              (nsIDNSService::RESOLVE_PRIORITY_MEDIUM |
+                               nsIDNSService::RESOLVE_SPECULATE),
+                              mDNSListener, nullptr,
+                              getter_AddRefs(tmpCancelable));
+    predicted = true;
+    if (verifier) {
+      PREDICTOR_LOG(("    sending preresolve verification"));
+      verifier->OnPredictDNS(uri);
+    }
+  }
+
+  return predicted;
+}
+
+// Find out if a top-level page is likely to redirect.
+bool
+Predictor::WouldRedirect(nsICacheEntry *entry, uint32_t loadCount,
+                         uint32_t lastLoad, int32_t globalDegradation,
+                         nsIURI **redirectURI)
+{
+  // TODO - not doing redirects for first go around
+  MOZ_ASSERT(NS_IsMainThread());
+
+  return false;
+}
+
+// Called from the main thread to update the database
+NS_IMETHODIMP
+Predictor::Learn(nsIURI *targetURI, nsIURI *sourceURI,
+                 PredictorLearnReason reason,
+                 nsILoadContext *loadContext)
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Predictor interface methods must be called on the main thread");
+
+  PREDICTOR_LOG(("Predictor::Learn"));
+
+  if (IsNeckoChild()) {
+    MOZ_DIAGNOSTIC_ASSERT(gNeckoChild);
+
+    PREDICTOR_LOG(("    called on child process"));
+
+    ipc::URIParams serTargetURI;
+    SerializeURI(targetURI, serTargetURI);
+
+    ipc::OptionalURIParams serSourceURI;
+    SerializeURI(sourceURI, serSourceURI);
+
+    IPC::SerializedLoadContext serLoadContext;
+    serLoadContext.Init(loadContext);
+
+    PREDICTOR_LOG(("    forwarding to parent"));
+    gNeckoChild->SendPredLearn(serTargetURI, serSourceURI, reason,
+                               serLoadContext);
+    return NS_OK;
+  }
+
+  PREDICTOR_LOG(("    called on parent process"));
+
+  if (!mInitialized) {
+    PREDICTOR_LOG(("    not initialized"));
+    return NS_OK;
+  }
+
+  if (!mEnabled) {
+    PREDICTOR_LOG(("    not enabled"));
+    return NS_OK;
+  }
+
+  if (loadContext && loadContext->UsePrivateBrowsing()) {
+    // Don't want to do anything in PB mode
+    PREDICTOR_LOG(("    in PB mode"));
+    return NS_OK;
+  }
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    PREDICTOR_LOG(("    got non-HTTP[S] URI"));
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  nsCOMPtr<nsIURI> targetOrigin;
+  nsCOMPtr<nsIURI> sourceOrigin;
+  nsCOMPtr<nsIURI> uriKey;
+  nsCOMPtr<nsIURI> originKey;
+  nsresult rv;
+
+  switch (reason) {
+  case nsINetworkPredictor::LEARN_LOAD_TOPLEVEL:
+    if (!targetURI || sourceURI) {
+      PREDICTOR_LOG(("    load toplevel invalid URI state"));
+      return NS_ERROR_INVALID_ARG;
+    }
+    rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin), mIOService);
+    NS_ENSURE_SUCCESS(rv, rv);
+    uriKey = targetURI;
+    originKey = targetOrigin;
+    break;
+  case nsINetworkPredictor::LEARN_STARTUP:
+    if (!targetURI || sourceURI) {
+      PREDICTOR_LOG(("    startup invalid URI state"));
+      return NS_ERROR_INVALID_ARG;
+    }
+    rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin), mIOService);
+    NS_ENSURE_SUCCESS(rv, rv);
+    uriKey = mStartupURI;
+    originKey = mStartupURI;
+    break;
+  case nsINetworkPredictor::LEARN_LOAD_REDIRECT:
+  case nsINetworkPredictor::LEARN_LOAD_SUBRESOURCE:
+    if (!targetURI || !sourceURI) {
+      PREDICTOR_LOG(("    redirect/subresource invalid URI state"));
+      return NS_ERROR_INVALID_ARG;
+    }
+    rv = ExtractOrigin(targetURI, getter_AddRefs(targetOrigin), mIOService);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = ExtractOrigin(sourceURI, getter_AddRefs(sourceOrigin), mIOService);
+    NS_ENSURE_SUCCESS(rv, rv);
+    uriKey = sourceURI;
+    originKey = sourceOrigin;
+    break;
+  default:
+    PREDICTOR_LOG(("    invalid reason"));
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  Telemetry::AutoCounter<Telemetry::PREDICTOR_LEARN_ATTEMPTS> learnAttempts;
+  ++learnAttempts;
+
+  Predictor::Reason argReason;
+  argReason.mLearn = reason;
+
+  // We always open the full uri (general cache) entry first, so we don't gum up
+  // the works waiting on predictor-only entries to open
+  RefPtr<Predictor::Action> uriAction =
+    new Predictor::Action(Predictor::Action::IS_FULL_URI,
+                          Predictor::Action::DO_LEARN, argReason, targetURI,
+                          sourceURI, nullptr, this);
+  nsAutoCString uriKeyStr, targetUriStr, sourceUriStr;
+  uriKey->GetAsciiSpec(uriKeyStr);
+  targetURI->GetAsciiSpec(targetUriStr);
+  if (sourceURI) {
+    sourceURI->GetAsciiSpec(sourceUriStr);
+  }
+  PREDICTOR_LOG(("    Learn uriKey=%s targetURI=%s sourceURI=%s reason=%d "
+                 "action=%p", uriKeyStr.get(), targetUriStr.get(),
+                 sourceUriStr.get(), reason, uriAction.get()));
+  // For learning full URI things, we *always* open readonly and secretly, as we
+  // rely on actual pageloads to update the entry's metadata for us.
+  uint32_t uriOpenFlags = nsICacheStorage::OPEN_READONLY |
+                          nsICacheStorage::OPEN_SECRETLY |
+                          nsICacheStorage::CHECK_MULTITHREADED;
+  if (reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL) {
+    // Learning for toplevel we want to open the full uri entry priority, since
+    // it's likely this entry will be used soon anyway, and we want this to be
+    // opened ASAP.
+    uriOpenFlags |= nsICacheStorage::OPEN_PRIORITY;
+  }
+  mCacheDiskStorage->AsyncOpenURI(uriKey, EmptyCString(), uriOpenFlags,
+                                  uriAction);
+
+  // Now we open the origin-only (and therefore predictor-only) entry
+  RefPtr<Predictor::Action> originAction =
+    new Predictor::Action(Predictor::Action::IS_ORIGIN,
+                          Predictor::Action::DO_LEARN, argReason, targetOrigin,
+                          sourceOrigin, nullptr, this);
+  nsAutoCString originKeyStr, targetOriginStr, sourceOriginStr;
+  originKey->GetAsciiSpec(originKeyStr);
+  targetOrigin->GetAsciiSpec(targetOriginStr);
+  if (sourceOrigin) {
+    sourceOrigin->GetAsciiSpec(sourceOriginStr);
+  }
+  PREDICTOR_LOG(("    Learn originKey=%s targetOrigin=%s sourceOrigin=%s reason=%d "
+                 "action=%p", originKeyStr.get(), targetOriginStr.get(),
+                 sourceOriginStr.get(), reason, originAction.get()));
+  uint32_t originOpenFlags;
+  if (reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL) {
+    // This is the only case when we want to update the 'last used' metadata on
+    // the cache entry we're getting. This only applies to predictor-specific
+    // entries.
+    originOpenFlags = nsICacheStorage::OPEN_NORMALLY |
+                      nsICacheStorage::CHECK_MULTITHREADED;
+  } else {
+    originOpenFlags = nsICacheStorage::OPEN_READONLY |
+                      nsICacheStorage::OPEN_SECRETLY |
+                      nsICacheStorage::CHECK_MULTITHREADED;
+  }
+  mCacheDiskStorage->AsyncOpenURI(originKey,
+                                  NS_LITERAL_CSTRING(PREDICTOR_ORIGIN_EXTENSION),
+                                  originOpenFlags, originAction);
+
+  PREDICTOR_LOG(("Predictor::Learn returning"));
+  return NS_OK;
+}
+
+void
+Predictor::LearnInternal(PredictorLearnReason reason, nsICacheEntry *entry,
+                         bool isNew, bool fullUri, nsIURI *targetURI,
+                         nsIURI *sourceURI)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::LearnInternal"));
+
+  nsCString junk;
+  if (!fullUri && reason == nsINetworkPredictor::LEARN_LOAD_TOPLEVEL &&
+      NS_FAILED(entry->GetMetaDataElement(SEEN_META_DATA, getter_Copies(junk)))) {
+    // This is an origin-only entry that we haven't seen before. Let's mark it
+    // as seen.
+    PREDICTOR_LOG(("    marking new origin entry as seen"));
+    nsresult rv = entry->SetMetaDataElement(SEEN_META_DATA, "1");
+    if (NS_FAILED(rv)) {
+      PREDICTOR_LOG(("    failed to mark origin entry seen"));
+      return;
+    }
+
+    // Need to ensure someone else can get to the entry if necessary
+    entry->MetaDataReady();
+    return;
+  }
+
+  switch (reason) {
+    case nsINetworkPredictor::LEARN_LOAD_TOPLEVEL:
+      // This case only exists to be used during tests - code outside the
+      // predictor tests should NEVER call Learn with LEARN_LOAD_TOPLEVEL.
+      // The predictor xpcshell test needs this branch, however, because we
+      // have no real page loads in xpcshell, and this is how we fake it up
+      // so that all the work that normally happens behind the scenes in a
+      // page load can be done for testing purposes.
+      if (fullUri && mDoingTests) {
+        PREDICTOR_LOG(("    WARNING - updating rolling load count. "
+                       "If you see this outside tests, you did it wrong"));
+        SanitizePrefs();
+
+        // Since the visitor gets called under a cache lock, all we do there is get
+        // copies of the keys/values we care about, and then do the real work here
+        entry->VisitMetaData(this);
+        nsTArray<nsCString> keysToOperateOn, valuesToOperateOn;
+        keysToOperateOn.SwapElements(mKeysToOperateOn);
+        valuesToOperateOn.SwapElements(mValuesToOperateOn);
+
+        MOZ_ASSERT(keysToOperateOn.Length() == valuesToOperateOn.Length());
+        for (size_t i = 0; i < keysToOperateOn.Length(); ++i) {
+          const char *key = keysToOperateOn[i].BeginReading();
+          const char *value = valuesToOperateOn[i].BeginReading();
+
+          nsCOMPtr<nsIURI> uri;
+          uint32_t hitCount, lastHit, flags;
+          if (!ParseMetaDataEntry(nullptr, value, nullptr, hitCount, lastHit, flags)) {
+            // This failed, get rid of it so we don't waste space
+            entry->SetMetaDataElement(key, nullptr);
+            continue;
+          }
+          UpdateRollingLoadCount(entry, flags, key, hitCount, lastHit);
+        }
+      } else {
+        PREDICTOR_LOG(("    nothing to do for toplevel"));
+      }
+      break;
+    case nsINetworkPredictor::LEARN_LOAD_REDIRECT:
+      if (fullUri) {
+        LearnForRedirect(entry, targetURI);
+      }
+      break;
+    case nsINetworkPredictor::LEARN_LOAD_SUBRESOURCE:
+      LearnForSubresource(entry, targetURI);
+      break;
+    case nsINetworkPredictor::LEARN_STARTUP:
+      LearnForStartup(entry, targetURI);
+      break;
+    default:
+      PREDICTOR_LOG(("    unexpected reason value"));
+      MOZ_ASSERT(false, "Got unexpected value for learn reason!");
+  }
+}
+
+NS_IMPL_ISUPPORTS(Predictor::SpaceCleaner, nsICacheEntryMetaDataVisitor)
+
+NS_IMETHODIMP
+Predictor::SpaceCleaner::OnMetaDataElement(const char *key, const char *value)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsURIMetadataElement(key)) {
+    // This isn't a bit of metadata we care about
+    return NS_OK;
+  }
+
+  uint32_t hitCount, lastHit, flags;
+  bool ok = mPredictor->ParseMetaDataEntry(nullptr, value, nullptr,
+                                           hitCount, lastHit, flags);
+
+  if (!ok) {
+    // Couldn't parse this one, just get rid of it
+    nsCString nsKey;
+    nsKey.AssignASCII(key);
+    mLongKeysToDelete.AppendElement(nsKey);
+    return NS_OK;
+  }
+
+  nsCString uri(key + (sizeof(META_DATA_PREFIX) - 1));
+  uint32_t uriLength = uri.Length();
+  if (uriLength > mPredictor->mMaxURILength) {
+    // Default to getting rid of URIs that are too long and were put in before
+    // we had our limit on URI length, in order to free up some space.
+    nsCString nsKey;
+    nsKey.AssignASCII(key);
+    mLongKeysToDelete.AppendElement(nsKey);
+    return NS_OK;
+  }
+
+  if (!mLRUKeyToDelete || lastHit < mLRUStamp) {
+    mLRUKeyToDelete = key;
+    mLRUStamp = lastHit;
+  }
+
+  return NS_OK;
+}
+
+void
+Predictor::SpaceCleaner::Finalize(nsICacheEntry *entry)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (mLRUKeyToDelete) {
+    entry->SetMetaDataElement(mLRUKeyToDelete, nullptr);
+  }
+
+  for (size_t i = 0; i < mLongKeysToDelete.Length(); ++i) {
+    entry->SetMetaDataElement(mLongKeysToDelete[i].BeginReading(), nullptr);
+  }
+}
+
+// Called when a subresource has been hit from a top-level load. Uses the two
+// helper functions above to update the database appropriately.
+void
+Predictor::LearnForSubresource(nsICacheEntry *entry, nsIURI *targetURI)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::LearnForSubresource"));
+
+  uint32_t lastLoad;
+  nsresult rv = entry->GetLastFetched(&lastLoad);
+  RETURN_IF_FAILED(rv);
+
+  int32_t loadCount;
+  rv = entry->GetFetchCount(&loadCount);
+  RETURN_IF_FAILED(rv);
+
+  nsCString key;
+  key.AssignLiteral(META_DATA_PREFIX);
+  nsCString uri;
+  targetURI->GetAsciiSpec(uri);
+  key.Append(uri);
+  if (uri.Length() > mMaxURILength) {
+    // We do this to conserve space/prevent OOMs
+    PREDICTOR_LOG(("    uri too long!"));
+    entry->SetMetaDataElement(key.BeginReading(), nullptr);
+    return;
+  }
+
+  nsCString value;
+  rv = entry->GetMetaDataElement(key.BeginReading(), getter_Copies(value));
+
+  uint32_t hitCount, lastHit, flags;
+  bool isNewResource = (NS_FAILED(rv) ||
+                        !ParseMetaDataEntry(nullptr, value.BeginReading(),
+                                            nullptr, hitCount, lastHit, flags));
+
+  int32_t resourceCount = 0;
+  if (isNewResource) {
+    // This is a new addition
+    PREDICTOR_LOG(("    new resource"));
+    nsCString s;
+    rv = entry->GetMetaDataElement(RESOURCE_META_DATA, getter_Copies(s));
+    if (NS_SUCCEEDED(rv)) {
+      resourceCount = atoi(s.BeginReading());
+    }
+    if (resourceCount >= mMaxResourcesPerEntry) {
+      RefPtr<Predictor::SpaceCleaner> cleaner =
+        new Predictor::SpaceCleaner(this);
+      entry->VisitMetaData(cleaner);
+      cleaner->Finalize(entry);
+    } else {
+      ++resourceCount;
+    }
+    nsAutoCString count;
+    count.AppendInt(resourceCount);
+    rv = entry->SetMetaDataElement(RESOURCE_META_DATA, count.BeginReading());
+    if (NS_FAILED(rv)) {
+      PREDICTOR_LOG(("    failed to update resource count"));
+      return;
+    }
+    hitCount = 1;
+    flags = 0;
+  } else {
+    PREDICTOR_LOG(("    existing resource"));
+    hitCount = std::min(hitCount + 1, static_cast<uint32_t>(loadCount));
+  }
+
+  // Update the rolling load count to mark this sub-resource as seen on the
+  // most-recent pageload so it can be eligible for prefetch (assuming all
+  // the other stars align).
+  flags |= (1 << kRollingLoadOffset);
+
+  nsCString newValue;
+  MakeMetadataEntry(hitCount, lastLoad, flags, newValue);
+  rv = entry->SetMetaDataElement(key.BeginReading(), newValue.BeginReading());
+  PREDICTOR_LOG(("    SetMetaDataElement -> 0x%08X", rv));
+  if (NS_FAILED(rv) && isNewResource) {
+    // Roll back the increment to the resource count we made above.
+    PREDICTOR_LOG(("    rolling back resource count update"));
+    --resourceCount;
+    if (resourceCount == 0) {
+      entry->SetMetaDataElement(RESOURCE_META_DATA, nullptr);
+    } else {
+      nsAutoCString count;
+      count.AppendInt(resourceCount);
+      entry->SetMetaDataElement(RESOURCE_META_DATA, count.BeginReading());
+    }
+  }
+}
+
+// This is called when a top-level loaded ended up redirecting to a different
+// URI so we can keep track of that fact.
+void
+Predictor::LearnForRedirect(nsICacheEntry *entry, nsIURI *targetURI)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // TODO - not doing redirects for first go around
+  PREDICTOR_LOG(("Predictor::LearnForRedirect"));
+}
+
+// This will add a page to our list of startup pages if it's being loaded
+// before our startup window has expired.
+void
+Predictor::MaybeLearnForStartup(nsIURI *uri, bool fullUri)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // TODO - not doing startup for first go around
+  PREDICTOR_LOG(("Predictor::MaybeLearnForStartup"));
+}
+
+// Add information about a top-level load to our list of startup pages
+void
+Predictor::LearnForStartup(nsICacheEntry *entry, nsIURI *targetURI)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // These actually do the same set of work, just on different entries, so we
+  // can pass through to get the real work done here
+  PREDICTOR_LOG(("Predictor::LearnForStartup"));
+  LearnForSubresource(entry, targetURI);
+}
+
+bool
+Predictor::ParseMetaDataEntry(const char *key, const char *value, nsIURI **uri,
+                              uint32_t &hitCount, uint32_t &lastHit,
+                              uint32_t &flags)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  PREDICTOR_LOG(("Predictor::ParseMetaDataEntry key=%s value=%s",
+                 key ? key : "", value));
+
+  const char *comma = strchr(value, ',');
+  if (!comma) {
+    PREDICTOR_LOG(("    could not find first comma"));
+    return false;
+  }
+
+  uint32_t version = static_cast<uint32_t>(atoi(value));
+  PREDICTOR_LOG(("    version -> %u", version));
+
+  if (version != METADATA_VERSION) {
+    PREDICTOR_LOG(("    metadata version mismatch %u != %u", version,
+                   METADATA_VERSION));
+    return false;
+  }
+
+  value = comma + 1;
+  comma = strchr(value, ',');
+  if (!comma) {
+    PREDICTOR_LOG(("    could not find second comma"));
+    return false;
+  }
+
+  hitCount = static_cast<uint32_t>(atoi(value));
+  PREDICTOR_LOG(("    hitCount -> %u", hitCount));
+
+  value = comma + 1;
+  comma = strchr(value, ',');
+  if (!comma) {
+    PREDICTOR_LOG(("    could not find third comma"));
+    return false;
+  }
+
+  lastHit = static_cast<uint32_t>(atoi(value));
+  PREDICTOR_LOG(("    lastHit -> %u", lastHit));
+
+  value = comma + 1;
+  flags = static_cast<uint32_t>(atoi(value));
+  PREDICTOR_LOG(("    flags -> %u", flags));
+
+  if (key) {
+    const char *uriStart = key + (sizeof(META_DATA_PREFIX) - 1);
+    nsresult rv = NS_NewURI(uri, uriStart, nullptr, mIOService);
+    if (NS_FAILED(rv)) {
+      PREDICTOR_LOG(("    NS_NewURI returned 0x%X", rv));
+      return false;
+    }
+    PREDICTOR_LOG(("    uri -> %s", uriStart));
+  }
+
+  return true;
+}
+
+NS_IMETHODIMP
+Predictor::Reset()
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Predictor interface methods must be called on the main thread");
+
+  PREDICTOR_LOG(("Predictor::Reset"));
+
+  if (IsNeckoChild()) {
+    MOZ_DIAGNOSTIC_ASSERT(gNeckoChild);
+
+    PREDICTOR_LOG(("    forwarding to parent process"));
+    gNeckoChild->SendPredReset();
+    return NS_OK;
+  }
+
+  PREDICTOR_LOG(("    called on parent process"));
+
+  if (!mInitialized) {
+    PREDICTOR_LOG(("    not initialized"));
+    return NS_OK;
+  }
+
+  if (!mEnabled) {
+    PREDICTOR_LOG(("    not enabled"));
+    return NS_OK;
+  }
+
+  RefPtr<Predictor::Resetter> reset = new Predictor::Resetter(this);
+  PREDICTOR_LOG(("    created a resetter"));
+  mCacheDiskStorage->AsyncVisitStorage(reset, true);
+  PREDICTOR_LOG(("    Cache async launched, returning now"));
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(Predictor::Resetter,
+                  nsICacheEntryOpenCallback,
+                  nsICacheEntryMetaDataVisitor,
+                  nsICacheStorageVisitor);
+
+Predictor::Resetter::Resetter(Predictor *predictor)
+  :mEntriesToVisit(0)
+  ,mPredictor(predictor)
+{ }
+
+NS_IMETHODIMP
+Predictor::Resetter::OnCacheEntryCheck(nsICacheEntry *entry,
+                                       nsIApplicationCache *appCache,
+                                       uint32_t *result)
+{
+  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Resetter::OnCacheEntryAvailable(nsICacheEntry *entry, bool isNew,
+                                           nsIApplicationCache *appCache,
+                                           nsresult result)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (NS_FAILED(result)) {
+    // This can happen when we've tried to open an entry that doesn't exist for
+    // some non-reset operation, and then get reset shortly thereafter (as
+    // happens in some of our tests).
+    --mEntriesToVisit;
+    if (!mEntriesToVisit) {
+      Complete();
+    }
+    return NS_OK;
+  }
+
+  entry->VisitMetaData(this);
+  nsTArray<nsCString> keysToDelete;
+  keysToDelete.SwapElements(mKeysToDelete);
+
+  for (size_t i = 0; i < keysToDelete.Length(); ++i) {
+    const char *key = keysToDelete[i].BeginReading();
+    entry->SetMetaDataElement(key, nullptr);
+  }
+
+  --mEntriesToVisit;
+  if (!mEntriesToVisit) {
+    Complete();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Resetter::OnMetaDataElement(const char *asciiKey,
+                                       const char *asciiValue)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!StringBeginsWith(nsDependentCString(asciiKey),
+                        NS_LITERAL_CSTRING(META_DATA_PREFIX))) {
+    // Not a metadata entry we care about, carry on
+    return NS_OK;
+  }
+
+  nsCString key;
+  key.AssignASCII(asciiKey);
+  mKeysToDelete.AppendElement(key);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Resetter::OnCacheStorageInfo(uint32_t entryCount, uint64_t consumption,
+                                        uint64_t capacity, nsIFile *diskDirectory)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Resetter::OnCacheEntryInfo(nsIURI *uri, const nsACString &idEnhance,
+                                      int64_t dataSize, int32_t fetchCount,
+                                      uint32_t lastModifiedTime, uint32_t expirationTime,
+                                      bool aPinned)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // The predictor will only ever touch entries with no idEnhance ("") or an
+  // idEnhance of PREDICTOR_ORIGIN_EXTENSION, so we filter out any entries that
+  // don't match that to avoid doing extra work.
+  if (idEnhance.EqualsLiteral(PREDICTOR_ORIGIN_EXTENSION)) {
+    // This is an entry we own, so we can just doom it entirely
+    mPredictor->mCacheDiskStorage->AsyncDoomURI(uri, idEnhance, nullptr);
+  } else if (idEnhance.IsEmpty()) {
+    // This is an entry we don't own, so we have to be a little more careful and
+    // just get rid of our own metadata entries. Append it to an array of things
+    // to operate on and then do the operations later so we don't end up calling
+    // Complete() multiple times/too soon.
+    ++mEntriesToVisit;
+    mURIsToVisit.AppendElement(uri);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::Resetter::OnCacheEntryVisitCompleted()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsTArray<nsCOMPtr<nsIURI>> urisToVisit;
+  urisToVisit.SwapElements(mURIsToVisit);
+
+  MOZ_ASSERT(mEntriesToVisit == urisToVisit.Length());
+  if (!mEntriesToVisit) {
+    Complete();
+    return NS_OK;
+  }
+
+  uint32_t entriesToVisit = urisToVisit.Length();
+  for (uint32_t i = 0; i < entriesToVisit; ++i) {
+    nsCString u;
+    urisToVisit[i]->GetAsciiSpec(u);
+    mPredictor->mCacheDiskStorage->AsyncOpenURI(
+        urisToVisit[i], EmptyCString(),
+        nsICacheStorage::OPEN_READONLY | nsICacheStorage::OPEN_SECRETLY | nsICacheStorage::CHECK_MULTITHREADED,
+        this);
+  }
+
+  return NS_OK;
+}
+
+void
+Predictor::Resetter::Complete()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (!obs) {
+    PREDICTOR_LOG(("COULD NOT GET OBSERVER SERVICE!"));
+    return;
+  }
+
+  obs->NotifyObservers(nullptr, "predictor-reset-complete", nullptr);
+}
+
+// Helper functions to make using the predictor easier from native code
+
+static nsresult
+EnsureGlobalPredictor(nsINetworkPredictor **aPredictor)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsresult rv;
+  nsCOMPtr<nsINetworkPredictor> predictor =
+    do_GetService("@mozilla.org/network/predictor;1",
+                  &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  predictor.forget(aPredictor);
+  return NS_OK;
+}
+
+nsresult
+PredictorPredict(nsIURI *targetURI, nsIURI *sourceURI,
+                 PredictorPredictReason reason, nsILoadContext *loadContext,
+                 nsINetworkPredictorVerifier *verifier)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsINetworkPredictor> predictor;
+  nsresult rv = EnsureGlobalPredictor(getter_AddRefs(predictor));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return predictor->Predict(targetURI, sourceURI, reason,
+                            loadContext, verifier);
+}
+
+nsresult
+PredictorLearn(nsIURI *targetURI, nsIURI *sourceURI,
+               PredictorLearnReason reason,
+               nsILoadContext *loadContext)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsINetworkPredictor> predictor;
+  nsresult rv = EnsureGlobalPredictor(getter_AddRefs(predictor));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return predictor->Learn(targetURI, sourceURI, reason, loadContext);
+}
+
+nsresult
+PredictorLearn(nsIURI *targetURI, nsIURI *sourceURI,
+               PredictorLearnReason reason,
+               nsILoadGroup *loadGroup)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsINetworkPredictor> predictor;
+  nsresult rv = EnsureGlobalPredictor(getter_AddRefs(predictor));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsILoadContext> loadContext;
+
+  if (loadGroup) {
+    nsCOMPtr<nsIInterfaceRequestor> callbacks;
+    loadGroup->GetNotificationCallbacks(getter_AddRefs(callbacks));
+    if (callbacks) {
+      loadContext = do_GetInterface(callbacks);
+    }
+  }
+
+  return predictor->Learn(targetURI, sourceURI, reason, loadContext);
+}
+
+nsresult
+PredictorLearn(nsIURI *targetURI, nsIURI *sourceURI,
+               PredictorLearnReason reason,
+               nsIDocument *document)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsINetworkPredictor> predictor;
+  nsresult rv = EnsureGlobalPredictor(getter_AddRefs(predictor));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsILoadContext> loadContext;
+
+  if (document) {
+    loadContext = document->GetLoadContext();
+  }
+
+  return predictor->Learn(targetURI, sourceURI, reason, loadContext);
+}
+
+nsresult
+PredictorLearnRedirect(nsIURI *targetURI, nsIChannel *channel,
+                       nsILoadContext *loadContext)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsCOMPtr<nsIURI> sourceURI;
+  nsresult rv = channel->GetOriginalURI(getter_AddRefs(sourceURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  bool sameUri;
+  rv = targetURI->Equals(sourceURI, &sameUri);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (sameUri) {
+    return NS_OK;
+  }
+
+  if (!IsNullOrHttp(targetURI) || !IsNullOrHttp(sourceURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsINetworkPredictor> predictor;
+  rv = EnsureGlobalPredictor(getter_AddRefs(predictor));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return predictor->Learn(targetURI, sourceURI,
+                          nsINetworkPredictor::LEARN_LOAD_REDIRECT,
+                          loadContext);
+}
+
+// nsINetworkPredictorVerifier
+
+/**
+ * Call through to the child's verifier (only during tests)
+ */
+NS_IMETHODIMP
+Predictor::OnPredictPrefetch(nsIURI *aURI, uint32_t httpStatus)
+{
+  if (IsNeckoChild()) {
+    if (mChildVerifier) {
+      // Ideally, we'd assert here. But since we're slowly moving towards a
+      // world where we have multiple child processes, and only one child process
+      // will be likely to have a verifier, we have to play it safer.
+      return mChildVerifier->OnPredictPrefetch(aURI, httpStatus);
+    }
+    return NS_OK;
+  }
+
+  ipc::URIParams serURI;
+  SerializeURI(aURI, serURI);
+
+  for (auto* cp : ContentParent::AllProcesses(ContentParent::eLive)) {
+    PNeckoParent* neckoParent = SingleManagedOrNull(cp->ManagedPNeckoParent());
+    if (!neckoParent) {
+      continue;
+    }
+    if (!neckoParent->SendPredOnPredictPrefetch(serURI, httpStatus)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::OnPredictPreconnect(nsIURI *aURI) {
+  if (IsNeckoChild()) {
+    if (mChildVerifier) {
+      // Ideally, we'd assert here. But since we're slowly moving towards a
+      // world where we have multiple child processes, and only one child process
+      // will be likely to have a verifier, we have to play it safer.
+      return mChildVerifier->OnPredictPreconnect(aURI);
+    }
+    return NS_OK;
+  }
+
+  ipc::URIParams serURI;
+  SerializeURI(aURI, serURI);
+
+  for (auto* cp : ContentParent::AllProcesses(ContentParent::eLive)) {
+    PNeckoParent* neckoParent = SingleManagedOrNull(cp->ManagedPNeckoParent());
+    if (!neckoParent) {
+      continue;
+    }
+    if (!neckoParent->SendPredOnPredictPreconnect(serURI)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::OnPredictDNS(nsIURI *aURI) {
+  if (IsNeckoChild()) {
+    if (mChildVerifier) {
+      // Ideally, we'd assert here. But since we're slowly moving towards a
+      // world where we have multiple child processes, and only one child process
+      // will be likely to have a verifier, we have to play it safer.
+      return mChildVerifier->OnPredictDNS(aURI);
+    }
+    return NS_OK;
+  }
+
+  ipc::URIParams serURI;
+  SerializeURI(aURI, serURI);
+
+  for (auto* cp : ContentParent::AllProcesses(ContentParent::eLive)) {
+    PNeckoParent* neckoParent = SingleManagedOrNull(cp->ManagedPNeckoParent());
+    if (!neckoParent) {
+      continue;
+    }
+    if (!neckoParent->SendPredOnPredictDNS(serURI)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  return NS_OK;
+}
+
+// Predictor::PrefetchListener
+// nsISupports
+NS_IMPL_ISUPPORTS(Predictor::PrefetchListener,
+                  nsIStreamListener,
+                  nsIRequestObserver)
+
+// nsIRequestObserver
+NS_IMETHODIMP
+Predictor::PrefetchListener::OnStartRequest(nsIRequest *aRequest,
+                                            nsISupports *aContext)
+{
+  mStartTime = TimeStamp::Now();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::PrefetchListener::OnStopRequest(nsIRequest *aRequest,
+                                           nsISupports *aContext,
+                                           nsresult aStatusCode)
+{
+  PREDICTOR_LOG(("OnStopRequest this=%p aStatusCode=0x%X", this, aStatusCode));
+  NS_ENSURE_ARG(aRequest);
+  if (NS_FAILED(aStatusCode)) {
+    return aStatusCode;
+  }
+  Telemetry::AccumulateTimeDelta(Telemetry::PREDICTOR_PREFETCH_TIME, mStartTime);
+
+  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aRequest);
+  if (!httpChannel) {
+    PREDICTOR_LOG(("    Could not get HTTP Channel!"));
+    return NS_ERROR_UNEXPECTED;
+  }
+  nsCOMPtr<nsICachingChannel> cachingChannel = do_QueryInterface(httpChannel);
+  if (!cachingChannel) {
+    PREDICTOR_LOG(("    Could not get caching channel!"));
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsresult rv = NS_OK;
+  uint32_t httpStatus;
+  rv = httpChannel->GetResponseStatus(&httpStatus);
+  if (NS_SUCCEEDED(rv) && httpStatus == 200) {
+    rv = cachingChannel->ForceCacheEntryValidFor(mPredictor->mPrefetchForceValidFor);
+    PREDICTOR_LOG(("    forcing entry valid for %d seconds rv=%X",
+                   mPredictor->mPrefetchForceValidFor, rv));
+  } else {
+    rv = cachingChannel->ForceCacheEntryValidFor(0);
+    PREDICTOR_LOG(("    removing any forced validity rv=%X", rv));
+  }
+
+  nsAutoCString reqName;
+  rv = aRequest->GetName(reqName);
+  if (NS_FAILED(rv)) {
+    reqName.AssignLiteral("<unknown>");
+  }
+
+  PREDICTOR_LOG(("    request %s status %u", reqName.get(), httpStatus));
+
+  if (mVerifier) {
+    mVerifier->OnPredictPrefetch(mURI, httpStatus);
+  }
+
+  return rv;
+}
+
+// nsIStreamListener
+NS_IMETHODIMP
+Predictor::PrefetchListener::OnDataAvailable(nsIRequest *aRequest,
+                                             nsISupports *aContext,
+                                             nsIInputStream *aInputStream,
+                                             uint64_t aOffset,
+                                             const uint32_t aCount)
+{
+  uint32_t result;
+  return aInputStream->ReadSegments(NS_DiscardSegment, nullptr, aCount, &result);
+}
+
+// Miscellaneous Predictor
+
+void
+Predictor::UpdateCacheability(nsIURI *sourceURI, nsIURI *targetURI,
+                              uint32_t httpStatus,
+                              nsHttpRequestHead &requestHead,
+                              nsHttpResponseHead *responseHead,
+                              nsILoadContextInfo *lci)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (lci && lci->IsPrivate()) {
+    PREDICTOR_LOG(("Predictor::UpdateCacheability in PB mode - ignoring"));
+    return;
+  }
+
+  if (!sourceURI || !targetURI) {
+    PREDICTOR_LOG(("Predictor::UpdateCacheability missing source or target uri"));
+    return;
+  }
+
+  if (!IsNullOrHttp(sourceURI) || !IsNullOrHttp(targetURI)) {
+    PREDICTOR_LOG(("Predictor::UpdateCacheability non-http(s) uri"));
+    return;
+  }
+
+  RefPtr<Predictor> self = sSelf;
+  if (self) {
+    nsAutoCString method;
+    requestHead.Method(method);
+    self->UpdateCacheabilityInternal(sourceURI, targetURI, httpStatus,
+                                     method);
+  }
+}
+
+void
+Predictor::UpdateCacheabilityInternal(nsIURI *sourceURI, nsIURI *targetURI,
+                                      uint32_t httpStatus,
+                                      const nsCString &method)
+{
+  PREDICTOR_LOG(("Predictor::UpdateCacheability httpStatus=%u", httpStatus));
+
+  if (!mInitialized) {
+    PREDICTOR_LOG(("    not initialized"));
+    return;
+  }
+
+  if (!mEnabled) {
+    PREDICTOR_LOG(("    not enabled"));
+    return;
+  }
+
+  if (!mEnablePrefetch) {
+    PREDICTOR_LOG(("    prefetch not enabled"));
+    return;
+  }
+
+  uint32_t openFlags = nsICacheStorage::OPEN_READONLY |
+                       nsICacheStorage::OPEN_SECRETLY |
+                       nsICacheStorage::CHECK_MULTITHREADED;
+  RefPtr<Predictor::CacheabilityAction> action =
+    new Predictor::CacheabilityAction(targetURI, httpStatus, method, this);
+  nsAutoCString uri;
+  targetURI->GetAsciiSpec(uri);
+  PREDICTOR_LOG(("    uri=%s action=%p", uri.get(), action.get()));
+  mCacheDiskStorage->AsyncOpenURI(sourceURI, EmptyCString(), openFlags, action);
+}
+
+NS_IMPL_ISUPPORTS(Predictor::CacheabilityAction,
+                  nsICacheEntryOpenCallback,
+                  nsICacheEntryMetaDataVisitor);
+
+NS_IMETHODIMP
+Predictor::CacheabilityAction::OnCacheEntryCheck(nsICacheEntry *entry,
+                                                 nsIApplicationCache *appCache,
+                                                 uint32_t *result)
+{
+  *result = nsICacheEntryOpenCallback::ENTRY_WANTED;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::CacheabilityAction::OnCacheEntryAvailable(nsICacheEntry *entry,
+                                                     bool isNew,
+                                                     nsIApplicationCache *appCache,
+                                                     nsresult result)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  // This is being opened read-only, so isNew should always be false
+  MOZ_ASSERT(!isNew);
+
+  PREDICTOR_LOG(("CacheabilityAction::OnCacheEntryAvailable this=%p", this));
+  if (NS_FAILED(result)) {
+    // Nothing to do
+    PREDICTOR_LOG(("    nothing to do result=%X isNew=%d", result, isNew));
+    return NS_OK;
+  }
+
+  nsresult rv = entry->VisitMetaData(this);
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("    VisitMetaData returned %x", rv));
+    return NS_OK;
+  }
+
+  nsTArray<nsCString> keysToCheck, valuesToCheck;
+  keysToCheck.SwapElements(mKeysToCheck);
+  valuesToCheck.SwapElements(mValuesToCheck);
+
+  MOZ_ASSERT(keysToCheck.Length() == valuesToCheck.Length());
+  for (size_t i = 0; i < keysToCheck.Length(); ++i) {
+    const char *key = keysToCheck[i].BeginReading();
+    const char *value = valuesToCheck[i].BeginReading();
+    nsCOMPtr<nsIURI> uri;
+    uint32_t hitCount, lastHit, flags;
+
+    if (!mPredictor->ParseMetaDataEntry(key, value, getter_AddRefs(uri),
+                                        hitCount, lastHit, flags)) {
+      PREDICTOR_LOG(("    failed to parse key=%s value=%s", key, value));
+      continue;
+    }
+
+    bool eq = false;
+    if (NS_SUCCEEDED(uri->Equals(mTargetURI, &eq)) && eq) {
+      if (mHttpStatus == 200 && mMethod.EqualsLiteral("GET")) {
+        PREDICTOR_LOG(("    marking %s cacheable", key));
+        flags |= FLAG_PREFETCHABLE;
+      } else {
+        PREDICTOR_LOG(("    marking %s uncacheable", key));
+        flags &= ~FLAG_PREFETCHABLE;
+      }
+      nsCString newValue;
+      MakeMetadataEntry(hitCount, lastHit, flags, newValue);
+      entry->SetMetaDataElement(key, newValue.BeginReading());
+      break;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+Predictor::CacheabilityAction::OnMetaDataElement(const char *asciiKey,
+                                                 const char *asciiValue)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsURIMetadataElement(asciiKey)) {
+    return NS_OK;
+  }
+
+  nsCString key, value;
+  key.AssignASCII(asciiKey);
+  value.AssignASCII(asciiValue);
+  mKeysToCheck.AppendElement(key);
+  mValuesToCheck.AppendElement(value);
+
+  return NS_OK;
+}
+
+} // namespace net
+} // namespace mozilla