Replaced is_null() with is_valid in SurfaceId and related classes.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <Carbon/Carbon.h>
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
@@ skipping 1501 matching lines @@
                            ->GetDisplayNearestWindow(cocoa_view_)
                            .device_scale_factor();
   gfx::Point point_in_pixels = gfx::ConvertPointToPixel(scale_factor, point);
   cc::SurfaceId id =
       browser_compositor_->GetDelegatedFrameHost()->SurfaceIdAtPoint(
           delegate, point_in_pixels, transformed_point);
   *transformed_point = gfx::ConvertPointToDIP(scale_factor, *transformed_point);
 
   // It is possible that the renderer has not yet produced a surface, in which
   // case we return our current namespace.
-  if (id.is_null())
+  if (!id.is_valid())
     return GetFrameSinkId();
   return id.frame_sink_id();
 }
 
 bool RenderWidgetHostViewMac::ShouldRouteEvent(
     const WebInputEvent& event) const {
   // See also RenderWidgetHostViewAura::ShouldRouteEvent.
   // TODO(wjmaclean): Update this function if RenderWidgetHostViewMac implements
   // OnTouchEvent(), to match what we are doing in RenderWidgetHostViewAura.
   DCHECK(WebInputEvent::isMouseEventType(event.type) ||
@@ skipping 1883 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end