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

chrome/browser/chrome_page_zoom.cc

Index: chrome/browser/chrome_page_zoom.cc
diff --git a/chrome/browser/chrome_page_zoom.cc b/chrome/browser/chrome_page_zoom.cc
index 95ec05a5ccb0ec0f3cdd6160db94d83b18c0dd13..a76744cbd02726a014963ef561a07e13fc13b2d2 100644
--- a/chrome/browser/chrome_page_zoom.cc
+++ b/chrome/browser/chrome_page_zoom.cc
@@ -70,6 +70,11 @@ 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())->