Implement top controls show/hide functionality for main thread scrolling

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/AnimationEffect.idl',
             'animation/AnimationNode.idl',
@@ skipping 1516 matching lines @@
             'frame/Screen.h',
             'frame/Settings.cpp',
             'frame/SettingsDelegate.cpp',
             'frame/SettingsDelegate.h',
             'frame/SmartClip.cpp',
             'frame/SmartClip.h',
             'frame/SubresourceIntegrity.cpp',
             'frame/SubresourceIntegrity.h',
             'frame/SuspendableTimer.cpp',
             'frame/SuspendableTimer.h',
+            'frame/TopControls.cpp',
+            'frame/TopControls.h',
             'frame/UseCounter.cpp',
             'frame/csp/CSPDirectiveList.cpp',
             'frame/csp/CSPSource.cpp',
             'frame/csp/CSPSourceList.cpp',
             'frame/csp/ContentSecurityPolicy.cpp',
             'frame/csp/MediaListDirective.cpp',
             'frame/csp/SourceListDirective.cpp',
             'imagebitmap/ImageBitmapFactories.cpp',
             'imagebitmap/ImageBitmapFactories.h',
             'inspector/AsyncCallChain.cpp',
@@ skipping 2254 matching lines @@
             'rendering/RenderingTestHelper.h',
             'streams/ExclusiveStreamReaderTest.cpp',
             'streams/ReadableStreamTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }