Mac HiDPI: Fix scale factor on external display

content/browser/renderer_host/render_widget_host_view_mac.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <list>
 
@@ skipping 117 matching lines @@
   // Whether the previous mouse event was ignored due to hitTest check.
   BOOL mouseEventWasIgnored_;
 
   // Event monitor for gesture-end events.
   id endGestureMonitor_;
 
   // OpenGL Support:
 
   // recursive globalFrameDidChange protection:
   BOOL handlingGlobalFrameDidChange_;
+
+  // The scale factor of the display this view is in.
+  float deviceScaleFactor_;
 }
 
 @property(nonatomic, readonly) NSRange selectedRange;
 
 - (void)setCanBeKeyView:(BOOL)can;
 - (void)setTakesFocusOnlyOnMouseDown:(BOOL)b;
 - (void)setCloseOnDeactivate:(BOOL)b;
 - (void)setToolTipAtMousePoint:(NSString *)string;
 // True for always-on-top special windows (e.g. Balloons and Panels).
 - (BOOL)acceptsMouseEventsWhenInactive;
@@ skipping 312 matching lines @@
 
   // The current caret bounds.
   gfx::Rect caret_rect_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_