Web Animations: Properly report ComputedEffectTime::localTime

The localTime should still be reported when the timing is not in effect.

Bug: 827613
Change-Id: I3ed29988ed0869a5261e0d756f7fbc94c24f3d4c
Reviewed-on: https://chromium-review.googlesource.com/989655Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547699}

third_party/WebKit/LayoutTests/external/wpt/web-animations/timing-model/animation-effects/local-time-expected.txt

-This is a testharness.js-based test.
-FAIL Local time is current time for animation effects associated with an animation assert_equals: expected (number) -1000 but got (object) null
-PASS Local time is unresolved for animation effects not associated with an animation
-Harness: the test ran to completion.
-

third_party/WebKit/Source/core/animation/AnimationEffect.cpp

@@ -106,12 +106,16 @@ void AnimationEffect::getComputedTiming(
   computed_timing.setEndTime(EndTimeInternal() * 1000);
   computed_timing.setActiveDuration(ActiveDurationInternal() * 1000);
 
-  if (EnsureCalculated().is_in_effect) {
+  if (IsNull(EnsureCalculated().local_time)) {
+    computed_timing.setLocalTimeToNull();
+  } else {
     computed_timing.setLocalTime(EnsureCalculated().local_time * 1000);
+  }
+
+  if (EnsureCalculated().is_in_effect) {
     computed_timing.setProgress(EnsureCalculated().progress.value());
     computed_timing.setCurrentIteration(EnsureCalculated().current_iteration);
   } else {
-    computed_timing.setLocalTimeToNull();
     computed_timing.setProgressToNull();
     computed_timing.setCurrentIterationToNull();
   }

third_party/WebKit/Source/core/animation/AnimationEffect.h

@@ -166,7 +166,7 @@ class CORE_EXPORT AnimationEffect : public ScriptWrappable {
     bool is_current;
     bool is_in_effect;
     bool is_in_play;
-    double local_time;
+    double local_time = NullValue();
     double time_to_forwards_effect_change;
     double time_to_reverse_effect_change;
   } calculated_;