Communicate MT changes to impl-only scroll offset animations

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'ContentDecryptionModuleResult.h',
@@ skipping 129 matching lines @@
       'Widget.h',
       'WindowsKeyboardCodes.h',
       'animation/AnimationTranslationUtil.cpp',
       'animation/AnimationTranslationUtil.h',
       'animation/AnimationUtilities.h',
       'animation/CompositorAnimation.cpp',
       'animation/CompositorAnimation.h',
       'animation/CompositorAnimationCurve.cpp',
       'animation/CompositorAnimationCurve.h',
       'animation/CompositorAnimationDelegate.h',
+      'animation/CompositorAnimationHost.cpp',
+      'animation/CompositorAnimationHost.h',
       'animation/CompositorAnimationPlayer.cpp',
       'animation/CompositorAnimationPlayer.h',
       'animation/CompositorAnimationPlayerClient.cpp',
       'animation/CompositorAnimationPlayerClient.h',
       'animation/CompositorAnimationTimeline.cpp',
       'animation/CompositorAnimationTimeline.h',
       'animation/CompositorFilterAnimationCurve.cpp',
       'animation/CompositorFilterAnimationCurve.h',
       'animation/CompositorFilterKeyframe.cpp',
       'animation/CompositorFilterKeyframe.h',
@@ skipping 1158 matching lines @@
       ['OS!="mac"',
         {
           'platform_test_files': [
             'scroll/ScrollAnimatorTest.cpp',
           ],
         }
       ],
     ],
   },
 }