Moving all the PlatformEvent subclasses from core/platform to platform

Source/platform/blink_platform.gypi

 {
   'variables': {
     'platform_files': [
       'AsyncFileSystem.h',
       'Clock.cpp',
       'Clock.h',
       'ContentType.cpp',
       'ContentType.h',
       'DateComponents.cpp',
       'DateComponents.h',
@@ skipping 24 matching lines @@
       'NotImplemented.cpp',
       'NotImplemented.h',
       'PODArena.h',
       'PODFreeListArena.h',
       'PODInterval.h',
       'PODIntervalTree.h',
       'PODRedBlackTree.h',
       'Partitions.cpp',
       'Partitions.h',
       'PlatformEvent.h',
+      'PlatformGestureEvent.h',
+      'PlatformKeyboardEvent.cpp',
+      'PlatformKeyboardEvent.h',
+      'PlatformMouseEvent.h',
+      'PlatformTouchPoint.h',
+      'PlatformTouchEvent.h',
+      'PlatformWheelEvent.h',
       'PlatformThreadData.cpp',
       'PlatformThreadData.h',
       'PurgeableBuffer.cpp',
       'PurgeableBuffer.h',
       'SecureTextInput.cpp',
       'SecureTextInput.h',
       'SSLKeyGenerator.cpp',
       'SSLKeyGenerator.h',
       'SharedBuffer.cpp',
       'SharedBuffer.h',
@@ skipping 227 matching lines @@
       'geometry/RoundedRectTest.cpp',
       'geometry/RoundedRectTest.cpp',
       'testing/ArenaTestHelpers.h',
       'testing/TreeTestHelpers.cpp',
       'testing/TreeTestHelpers.h',
       'text/DateTimeFormatTest.cpp',
       'text/DateTimeFormatTest.cpp',
     ],
   },
 }