Make sure WebContents passed to chrome_page_zoom::Zoom() have a ZoomController.

chrome/browser/chrome_page_zoom.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 "chrome/browser/chrome_page_zoom.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/prefs/pref_service.h"
@@ skipping 51 matching lines @@
   return PresetZoomValues(PAGE_ZOOM_VALUE_TYPE_FACTOR, custom_factor);
 }
 
 std::vector<double> PresetZoomLevels(double custom_level) {
   return PresetZoomValues(PAGE_ZOOM_VALUE_TYPE_LEVEL, custom_level);
 }
 
 void Zoom(content::WebContents* web_contents, content::PageZoom zoom) {
   ZoomController* zoom_controller =
       ZoomController::FromWebContents(web_contents);
 

[Peter Kasting, 2014/07/08 19:16:42]

Nit: Extra blank line

[wjmaclean, 2014/07/08 20:51:21]

Done.

+  if (!zoom_controller) {
+    NOTREACHED();

[Peter Kasting, 2014/07/08 19:16:43]

This is banned by the style guide.  If |zoom_controller| can actually be NULL
here, remove the NOTREACHED().  If not, change to "DCHECK(zoom_controller);" and
eliminate the conditional return.  (I imagine you want the latter.)

[wjmaclean, 2014/07/08 20:51:21]

I was hoping to generate well-documented failures in debug builds while not
crashing release builds. Generally, zoom_controller should never be NULL, but
this is new behavior and we've already found at least one case we missed.

Converted to DCHECK.

[Peter Kasting, 2014/07/08 20:52:47]

Yeah, DCHECK is correct for what you describe.  The other option is to
temporarily make this a CHECK, if you decide crashing release builds is OK.

+    return;
+  }
+
   double current_zoom_level = zoom_controller->GetZoomLevel();
   double default_zoom_level =
       Profile::FromBrowserContext(web_contents->GetBrowserContext())->
           GetPrefs()->GetDouble(prefs::kDefaultZoomLevel);
 
   if (zoom == content::PAGE_ZOOM_RESET) {
     zoom_controller->SetZoomLevel(default_zoom_level);
     content::RecordAction(UserMetricsAction("ZoomNormal"));
     return;
   }
@@ skipping 29 matching lines @@
         zoom_controller->SetZoomLevel(zoom_level);
         content::RecordAction(UserMetricsAction("ZoomPlus"));
         return;
       }
     }
     content::RecordAction(UserMetricsAction("ZoomPlus_AtMaximum"));
   }
 }
 
 }  // namespace chrome_page_zoom