Mac: Fix renderer idle cpu usage regression.

chrome/browser/tab_contents/tab_contents_view_mac.mm

 // Copyright (c) 2010 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.
 
 #import <Carbon/Carbon.h>
 
 #include "chrome/browser/tab_contents/tab_contents_view_mac.h"
 
 #include <string>
 
@@ skipping 136 matching lines @@
   MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
   NSDragOperation mask = static_cast<NSDragOperation>(allowed_operations);
   NSPoint offset = NSPointFromCGPoint(image_offset.ToCGPoint());
   [cocoa_view_ startDragWithDropData:drop_data
                    dragOperationMask:mask
                                image:gfx::SkBitmapToNSImage(image)
                               offset:offset];
 }
 
 void TabContentsViewMac::RenderViewCreated(RenderViewHost* host) {
-  // We want updates whenever the intrinsic width of the webpage
-  // changes. Put the RenderView into that mode.
-  int routing_id = host->routing_id();
-  host->Send(new ViewMsg_EnablePreferredSizeChangedMode(routing_id));
+  // We want updates whenever the intrinsic width of the webpage changes.
+  // Put the RenderView into that mode. The preferred width is used for example
+  // when the "zoom" button in the browser window is clicked.
+  host->EnablePreferredSizeChangedMode(kPreferredSizeWidth);
 }
 
 void TabContentsViewMac::SetPageTitle(const std::wstring& title) {
   // Meaningless on the Mac; widgets don't have a "title" attribute
 }
 
 void TabContentsViewMac::OnTabCrashed() {
   if (!sad_tab_.get()) {
     TabContents* contents = tab_contents();
     DCHECK(contents);
@@ skipping 287 matching lines @@
   [NSObject cancelPreviousPerformRequestsWithTarget:self
                                            selector:aSel
                                              object:nil];
 }
 
 - (void)closeTabAfterEvent {
   tabContentsView_->CloseTab();
 }
 
 @end