Bug 1440195 Address CSS Animations r=birtles

For now, we are going to make _all_ CSS Animations related timer fuzzing
only applicable in Resist Fingerprinting Mode (addressing the last couple
that had not already been configured that way.)

We hardcode their content mix-ins as zero, but leave comments indicating
how they should behave.

MozReview-Commit-ID: KhmV7wO8Pt5

--HG--
extra : rebase_source : 3b087d40b6332d447b442b435ed6fee8993e0145

dom/animation/AnimationUtils.h

@@ -32,8 +32,12 @@ public:
     dom::Nullable<double> result;
 
     if (!aTime.IsNull()) {
+      // 0 is an inappropriate mixin for this this area; however CSS Animations needs to
+      // have it's Time Reduction Logic refactored, so it's currently only clamping for
+      // RFP mode. RFP mode gives a much lower time precision, so we accept the security
+      // leak here for now
       result.SetValue(
-        nsRFPService::ReduceTimePrecisionAsMSecs(aTime.Value().ToMilliseconds(), TimerPrecisionType::RFPOnly)
+        nsRFPService::ReduceTimePrecisionAsMSecs(aTime.Value().ToMilliseconds(), 0, TimerPrecisionType::RFPOnly)
       );
     }
 

layout/style/nsAnimationManager.cpp

@@ -246,7 +246,12 @@ CSSAnimation::QueueEvents(const StickyTimeDuration& aActiveTime)
                                   const TimeStamp& aTimeStamp) {
     double elapsedTime = aElapsedTime.ToSeconds();
     if (aMessage == eAnimationCancel) {
-      elapsedTime = nsRFPService::ReduceTimePrecisionAsSecs(elapsedTime);
+      // 0 is an inappropriate value for this callsite. What we need to do is
+      // use a single random value for all increasing times reportable.
+      // That is to say, whenever elapsedTime goes negative (because an
+      // animation restarts, something rewinds the animation, or otherwise)
+      // a new random value for the mix-in must be generated.
+      elapsedTime = nsRFPService::ReduceTimePrecisionAsSecs(elapsedTime, 0, TimerPrecisionType::RFPOnly);
     }
     events.AppendElement(AnimationEventInfo(mAnimationName,
                                             mOwningElement.Target(),

layout/style/nsTransitionManager.cpp

@@ -267,7 +267,12 @@ CSSTransition::QueueEvents(const StickyTimeDuration& aActiveTime)
                                    const TimeStamp& aTimeStamp) {
     double elapsedTime = aElapsedTime.ToSeconds();
     if (aMessage == eTransitionCancel) {
-      elapsedTime = nsRFPService::ReduceTimePrecisionAsSecs(elapsedTime);
+      // 0 is an inappropriate value for this callsite. What we need to do is
+      // use a single random value for all increasing times reportable.
+      // That is to say, whenever elapsedTime goes negative (because an
+      // animation restarts, something rewinds the animation, or otherwise)
+      // a new random value for the mix-in must be generated.
+      elapsedTime = nsRFPService::ReduceTimePrecisionAsSecs(elapsedTime, 0, TimerPrecisionType::RFPOnly);
     }
     events.AppendElement(AnimationEventInfo(TransitionProperty(),
                                             mOwningElement.Target(),