Remove PlatformEvent it is no longer used.

third_party/WebKit/Source/web/tests/WebPluginContainerTest.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #include "public/web/WebPluginContainer.h"
 
 #include <memory>
 #include <string>
 #include "core/dom/Element.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameHost.h"
 #include "core/layout/LayoutObject.h"
 #include "core/page/Page.h"
-#include "platform/PlatformEvent.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/graphics/paint/ForeignLayerDisplayItem.h"
 #include "platform/graphics/paint/PaintController.h"
 #include "platform/graphics/paint/PaintRecorder.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 #include "platform/testing/URLTestHelpers.h"
 #include "platform/testing/UnitTestHelpers.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebClipboard.h"
@@ skipping 734 matching lines @@
           WebString::fromUTF8("translated-plugin"));
   pluginContainerOneElement.pluginContainer()->setWantsWheelEvents(true);
 
   runPendingTasks();
   EXPECT_TRUE(
       webView->page()->frameHost().eventHandlerRegistry().hasEventHandlers(
           EventHandlerRegistry::WheelEventBlocking));
 }
 
 }  // namespace blink