Reland: Measure whether muted videos that started playing with play() become visible at some point

third_party/WebKit/Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/AnimationEffectReadOnly.idl',
             'animation/AnimationEffectTiming.idl',
@@ skipping 2880 matching lines @@
             'observer/ResizeObserver.cpp',
             'observer/ResizeObserverCallback.h',
             'observer/ResizeObserverController.h',
             'observer/ResizeObserverController.cpp',
             'observer/ResizeObserverEntry.h',
             'observer/ResizeObserverEntry.cpp',
         ],
         'webcore_html_files': [
             'html/AutoplayExperimentHelper.cpp',
             'html/AutoplayExperimentHelper.h',
+            'html/AutoplayUmaHelper.cpp',
+            'html/AutoplayUmaHelper.h',
             'html/ClassList.cpp',
             'html/ClassList.h',
             'html/CrossOriginAttribute.cpp',
             'html/CrossOriginAttribute.h',
             'html/DocumentNameCollection.cpp',
             'html/DocumentNameCollection.h',
             'html/FormAssociatedElement.cpp',
             'html/FormData.cpp',
             'html/FormData.h',
             'html/HTMLAllCollection.cpp',
@@ skipping 1364 matching lines @@
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'timing/PerformanceBaseTest.cpp',
             'timing/PerformanceObserverTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'workers/WorkerThreadTestHelper.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }