Support buttons attribute for drag event (blink side).

Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 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 223 matching lines @@
     virtual void dragSourceEndedAt(
         const WebPoint& clientPoint,
         const WebPoint& screenPoint,
         WebDragOperation) override;
     virtual void dragSourceSystemDragEnded() override;
     virtual WebDragOperation dragTargetDragEnter(
         const WebDragData&,
         const WebPoint& clientPoint,
         const WebPoint& screenPoint,
         WebDragOperationsMask operationsAllowed,
-        int keyModifiers) override;
+        int modifiers) override;
     virtual WebDragOperation dragTargetDragOver(
         const WebPoint& clientPoint,
         const WebPoint& screenPoint,
         WebDragOperationsMask operationsAllowed,
-        int keyModifiers) override;
+        int modifiers) override;
     virtual void dragTargetDragLeave() override;
     virtual void dragTargetDrop(
         const WebPoint& clientPoint,
         const WebPoint& screenPoint,
-        int keyModifiers) override;
+        int modifiers) override;
     virtual void spellingMarkers(WebVector<uint32_t>* markers) override;
     virtual void removeSpellingMarkersUnderWords(const WebVector<WebString>& words) override;
     virtual unsigned long createUniqueIdentifierForRequest() override;
     virtual void inspectElementAt(const WebPoint&) override;
     virtual void setCompositorDeviceScaleFactorOverride(float) override;
     virtual void setRootLayerTransform(const WebSize& offset, float scale) override;
     virtual WebDevToolsAgent* devToolsAgent() override;
     virtual WebAXObject accessibilityObject() override;
     virtual void setSelectionColors(unsigned activeBackgroundColor,
                                     unsigned activeForegroundColor,
@@ skipping 309 matching lines @@
     // Converts |pos| from window coordinates to contents coordinates and gets
     // the HitTestResult for it.
     HitTestResult hitTestResultForWindowPos(const IntPoint&);
 
     // Consolidate some common code between starting a drag over a target and
     // updating a drag over a target. If we're starting a drag, |isEntering|
     // should be true.
     WebDragOperation dragTargetDragEnterOrOver(const WebPoint& clientPoint,
                                                const WebPoint& screenPoint,
                                                DragAction,
-                                               int keyModifiers);
+                                               int modifiers);
 
     void configureAutoResizeMode();
 
     void initializeLayerTreeView();
 
     void setIsAcceleratedCompositingActive(bool);
     void doComposite();
     void reallocateRenderer();
     void updateLayerTreeViewport();
     void updateLayerTreeBackgroundColor();
@@ skipping 170 matching lines @@
 };
 
 DEFINE_TYPE_CASTS(WebViewImpl, WebWidget, widget, widget->isWebView(), widget.isWebView());
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 } // namespace blink
 
 #endif