Remove PlatformEvent it is no longer used.

third_party/WebKit/Source/web/WebFrameWidgetBase.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "web/WebFrameWidgetBase.h"
 
 #include "core/frame/FrameHost.h"
 #include "core/frame/VisualViewport.h"
 #include "core/input/EventHandler.h"
 #include "core/page/DragActions.h"
@@ skipping 120 matching lines @@
     cancelDrag();
     return;
   }
   WebFloatPoint pointInRootFrame(
       page()->frameHost().visualViewport().viewportToRootFrame(
           pointInViewport));
 
   WebMouseEvent fakeMouseMove(WebInputEvent::MouseMove, pointInRootFrame,
                               WebFloatPoint(screenPoint.x, screenPoint.y),
                               WebPointerProperties::Button::Left, 0,
-                              PlatformEvent::NoModifiers,
+                              WebInputEvent::NoModifiers,
                               TimeTicks::Now().InSeconds());
   fakeMouseMove.setFrameScale(1);
   toCoreFrame(localRoot())
       ->eventHandler()
       .dragSourceEndedAt(fakeMouseMove, static_cast<DragOperation>(operation));
 }
 
 void WebFrameWidgetBase::dragSourceSystemDragEnded() {
   cancelDrag();
 }
@@ skipping 57 matching lines @@
 
 WebViewImpl* WebFrameWidgetBase::view() const {
   return toWebLocalFrameImpl(localRoot())->viewImpl();
 }
 
 Page* WebFrameWidgetBase::page() const {
   return view()->page();
 }
 
 }  // namespace blink