Use the screen info's scale factor to scale the drag image

content/public/renderer/render_view.h

Index: content/public/renderer/render_view.h
diff --git a/content/public/renderer/render_view.h b/content/public/renderer/render_view.h
index baa051f155ef72b21e8668dd7099100bdeb6319a..5909ef39184482733346e6330b6c6019c2617fbe 100644
--- a/content/public/renderer/render_view.h
+++ b/content/public/renderer/render_view.h
@@ -75,6 +75,9 @@ class CONTENT_EXPORT RenderView : public IPC::Sender {
   // Returns the size of the view.
   virtual gfx::Size GetSize() const = 0;
 
+  // Returns the device scale factor of the display the render view is in.
+  virtual float GetDeviceScaleFactor() const = 0;
+
   // Gets WebKit related preferences associated with this view.
   virtual WebPreferences& GetWebkitPreferences() = 0;