Add use counters for function values of easing

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

Index: third_party/WebKit/Source/core/animation/AnimationEffectTiming.cpp
diff --git a/third_party/WebKit/Source/core/animation/AnimationEffectTiming.cpp b/third_party/WebKit/Source/core/animation/AnimationEffectTiming.cpp
index 55f811107c4b679502d647b3629b9eeacd35a519..8d784c02166b61daee1bd57a6e72cdfc9585ee34 100644
--- a/third_party/WebKit/Source/core/animation/AnimationEffectTiming.cpp
+++ b/third_party/WebKit/Source/core/animation/AnimationEffectTiming.cpp
@@ -130,7 +130,12 @@ void AnimationEffectTiming::setDirection(String direction)
 void AnimationEffectTiming::setEasing(String easing)
 {
     Timing timing = m_parent->specifiedTiming();
-    TimingInput::setTimingFunction(timing, easing);
+    // The AnimationEffectTiming might not be attached to a document at this
+    // point, so we pass nullptr in to setTimingFunction. This means that these
+    // calls are not considered in the WebAnimationsEasingAsFunction*
+    // UseCounters, but the bug we are tracking there does not come through
+    // this interface.
+    TimingInput::setTimingFunction(timing, easing, nullptr);
     m_parent->updateSpecifiedTiming(timing);
 }