CC Animation: Unify ElementId in Blink Compositor Worker.

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'ContentDecryptionModuleResult.h',
@@ skipping 546 matching lines @@
       'graphics/CanvasMetrics.cpp',
       'graphics/CanvasMetrics.h',
       'graphics/Color.cpp',
       'graphics/Color.h',
       'graphics/ColorSpace.cpp',
       'graphics/ColorSpace.h',
       'graphics/ColorSpaceProfileData.cpp',
       'graphics/ColorSpaceProfileData.h',
       'graphics/CompositingReasons.cpp',
       'graphics/CompositingReasons.h',
+      'graphics/CompositorElementId.h',
       'graphics/CompositorFactory.cpp',
       'graphics/CompositorFactory.h',
       'graphics/CompositorFilterOperations.cpp',
       'graphics/CompositorFilterOperations.h',
       'graphics/CompositorMutableState.cpp',
       'graphics/CompositorMutableState.h',
       'graphics/CompositorMutableStateProvider.cpp',
       'graphics/CompositorMutableStateProvider.h',
       'graphics/ContentLayerDelegate.cpp',
       'graphics/ContentLayerDelegate.h',
@@ skipping 741 matching lines @@
       ['OS!="mac"',
         {
           'platform_test_files': [
             'scroll/ScrollAnimatorTest.cpp',
           ],
         }
       ],
     ],
   },
 }