ZoomController: manual mode SetZoom() should early-out.

components/ui/zoom/zoom_controller.cc

 // 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 "components/ui/zoom/zoom_controller.h"
 
 #include "components/ui/zoom/zoom_event_manager.h"
 #include "components/ui/zoom/zoom_observer.h"
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/navigation_details.h"
@@ skipping 77 matching lines @@
       !web_contents()->GetRenderViewHost()->IsRenderViewLive())
     return false;
 
   // Store client data so the |client| can be attributed when the zoom
   // change completes. We expect that by the time this function returns that
   // any observers that require this information will have requested it.
   last_client_ = client;
 
   // Do not actually rescale the page in manual mode.
   if (zoom_mode_ == ZOOM_MODE_MANUAL) {
+    // If the zoom level hasn't changed, early out to avoid sending an event.
+    if (zoom_level_ == zoom_level)
+      return true;
+
     double old_zoom_level = zoom_level_;
     zoom_level_ = zoom_level;
 
     // TODO(wjmaclean) Do we care about filling in host/scheme here?
     content::HostZoomMap::ZoomLevelChange change;
     change.mode = content::HostZoomMap::ZOOM_CHANGED_TEMPORARY_ZOOM;
     change.zoom_level = zoom_level;
     ZoomEventManager::GetForBrowserContext(browser_context_)
         ->OnZoomLevelChanged(change);
 
@@ skipping 223 matching lines @@
     // new zoom levels here?
     double zoom_level = GetZoomLevel();
     ZoomChangedEventData zoom_change_data(
         web_contents(), zoom_level, zoom_level, zoom_mode_, can_show_bubble);
     FOR_EACH_OBSERVER(ZoomObserver, observers_,
                       OnZoomChanged(zoom_change_data));
   }
 }
 
 }  // namespace ui_zoom