Bug 1430173 - Reduce the precision of all explicit clocks to 2ms. r=baku, a=RyanVM

Backport to ESR where we don't have the ResistFingerprinting component.

MozReview-Commit-ID: 9bjycHjR3SF

--HG--
extra : transplant_source : %EA%03%21%0A%E9%3F%8E%CD%7C%D79f%96%85%96%00%5D%7F%95X

3 files changed, 27 insertions, 25 deletions

diff --git a/dom/performance/Performance.cpp b/dom/performance/Performance.cpp
index 17273c55d..8dc239b05 100644..100755
--- a/dom/performance/Performance.cpp
+++ b/dom/performance/Performance.cpp
@@ -21,6 +21,7 @@
 #include "mozilla/dom/PerformanceObserverBinding.h"
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/TimerClamping.h"
 #include "WorkerPrivate.h"
 #include "WorkerRunnable.h"
 
@@ -228,9 +229,9 @@ Performance::ClearResourceTimings()
 DOMHighResTimeStamp
 Performance::RoundTime(double aTime) const
 {
-  // Round down to the nearest 20us, because if the timer is too accurate people
+  // Round down to the nearest 2ms, because if the timer is too accurate people
   // can do nasty timing attacks with it.
-  const double maxResolutionMs = 0.020;
+  const double maxResolutionMs = 2;
   return floor(aTime / maxResolutionMs) * maxResolutionMs;
 }
 
diff --git a/dom/performance/PerformanceTiming.cpp b/dom/performance/PerformanceTiming.cpp
index 4070b6a0f..97bbcb0ca 100644..100755
--- a/dom/performance/PerformanceTiming.cpp
+++ b/dom/performance/PerformanceTiming.cpp
@@ -21,7 +21,7 @@ PerformanceTiming::PerformanceTiming(Performance* aPerformance,
                                      DOMHighResTimeStamp aZeroTime)
   : mPerformance(aPerformance),
     mFetchStart(0.0),
-    mZeroTime(aZeroTime),
+    mZeroTime(TimerClamping::ReduceMsTimeValue(aZeroTime)),
     mRedirectCount(0),
     mTimingAllowed(true),
     mAllRedirectsSameOrigin(true),
@@ -117,7 +117,7 @@ PerformanceTiming::FetchStartHighRes()
         ? TimeStampToDOMHighRes(mAsyncOpen)
         : 0.0;
   }
-  return mFetchStart;
+  return TimerClamping::ReduceMsTimeValue(mFetchStart);
 }
 
 DOMTimeMilliSec
@@ -203,7 +203,7 @@ PerformanceTiming::RedirectStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRedirectStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRedirectStart);
 }
 
 DOMTimeMilliSec
@@ -236,7 +236,7 @@ PerformanceTiming::RedirectEndHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRedirectEnd);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRedirectEnd);
 }
 
 DOMTimeMilliSec
@@ -259,7 +259,7 @@ PerformanceTiming::DomainLookupStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mDomainLookupStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mDomainLookupStart);
 }
 
 DOMTimeMilliSec
@@ -276,7 +276,7 @@ PerformanceTiming::DomainLookupEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return DomainLookupStart when null
   return mDomainLookupEnd.IsNull() ? DomainLookupStartHighRes()
-                                   : TimeStampToDOMHighRes(mDomainLookupEnd);
+                                   : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mDomainLookupEnd));
 }
 
 DOMTimeMilliSec
@@ -292,7 +292,7 @@ PerformanceTiming::ConnectStartHighRes()
     return mZeroTime;
   }
   return mConnectStart.IsNull() ? DomainLookupEndHighRes()
-                                : TimeStampToDOMHighRes(mConnectStart);
+                                : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mConnectStart));
 }
 
 DOMTimeMilliSec
@@ -329,7 +329,7 @@ PerformanceTiming::ConnectEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return ConnectStart when null
   return mConnectEnd.IsNull() ? ConnectStartHighRes()
-                              : TimeStampToDOMHighRes(mConnectEnd);
+                              : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mConnectEnd));
 }
 
 DOMTimeMilliSec
@@ -344,7 +344,7 @@ PerformanceTiming::RequestStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRequestStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRequestStart);
 }
 
 DOMTimeMilliSec
@@ -363,7 +363,7 @@ PerformanceTiming::ResponseStartHighRes()
      (!mCacheReadStart.IsNull() && mCacheReadStart < mResponseStart)) {
     mResponseStart = mCacheReadStart;
   }
-  return TimeStampToDOMHighResOrFetchStart(mResponseStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mResponseStart);
 }
 
 DOMTimeMilliSec
@@ -384,7 +384,7 @@ PerformanceTiming::ResponseEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return ResponseStart when null
   return mResponseEnd.IsNull() ? ResponseStartHighRes()
-                               : TimeStampToDOMHighRes(mResponseEnd);
+                               : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mResponseEnd));
 }
 
 DOMTimeMilliSec
diff --git a/dom/performance/PerformanceTiming.h b/dom/performance/PerformanceTiming.h
index 0bc73fd3f..edfac8d02 100644..100755
--- a/dom/performance/PerformanceTiming.h
+++ b/dom/performance/PerformanceTiming.h
@@ -10,6 +10,7 @@
 #include "mozilla/Attributes.h"
 #include "nsContentUtils.h"
 #include "nsDOMNavigationTiming.h"
+#include "mozilla/TimerClamping.h"
 #include "nsWrapperCache.h"
 #include "Performance.h"
 
@@ -68,10 +69,10 @@ public:
    *          page), if the given TimeStamp is valid. Otherwise, it will return
    *          the FetchStart timing value.
    */
-  inline DOMHighResTimeStamp TimeStampToDOMHighResOrFetchStart(TimeStamp aStamp)
+  inline DOMHighResTimeStamp TimeStampToReducedDOMHighResOrFetchStart(TimeStamp aStamp)
   {
     return (!aStamp.IsNull())
-        ? TimeStampToDOMHighRes(aStamp)
+        ? TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(aStamp))
         : FetchStartHighRes();
   }
 
@@ -119,7 +120,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetNavigationStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetNavigationStart());
   }
 
   DOMTimeMilliSec UnloadEventStart()
@@ -127,7 +128,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetUnloadEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetUnloadEventStart());
   }
 
   DOMTimeMilliSec UnloadEventEnd()
@@ -135,7 +136,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetUnloadEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetUnloadEventEnd());
   }
 
   uint16_t GetRedirectCount() const;
@@ -185,7 +186,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomLoading();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomLoading());
   }
 
   DOMTimeMilliSec DomInteractive() const
@@ -193,7 +194,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomInteractive();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomInteractive());
   }
 
   DOMTimeMilliSec DomContentLoadedEventStart() const
@@ -201,7 +202,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomContentLoadedEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomContentLoadedEventStart());
   }
 
   DOMTimeMilliSec DomContentLoadedEventEnd() const
@@ -209,7 +210,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomContentLoadedEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomContentLoadedEventEnd());
   }
 
   DOMTimeMilliSec DomComplete() const
@@ -217,7 +218,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomComplete();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomComplete());
   }
 
   DOMTimeMilliSec LoadEventStart() const
@@ -225,7 +226,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetLoadEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetLoadEventStart());
   }
 
   DOMTimeMilliSec LoadEventEnd() const
@@ -233,7 +234,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetLoadEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetLoadEventEnd());
   }
 
 private: