Don't assume WebContents has a LastCommittedEntry when setting zoom.

content/browser/host_zoom_map_impl.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 "content/browser/host_zoom_map_impl.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/strings/string_piece.h"
@@ skipping 229 matching lines @@
     double level) {
   int render_process_id = web_contents_impl.GetRenderProcessHost()->GetID();
   int render_view_id = web_contents_impl.GetRenderViewHost()->GetRoutingID();
   if (UsesTemporaryZoomLevel(render_process_id, render_view_id)) {
     SetTemporaryZoomLevel(render_process_id, render_view_id, level);
   } else {
     // Get the url from the navigation controller directly, as calling
     // WebContentsImpl::GetLastCommittedURL() may give us a virtual url that
     // is different than what the render view is using. If the two don't match,
     // the attempt to set the zoom will fail.
-    GURL url;
     NavigationEntry* entry =
         web_contents_impl.GetController().GetLastCommittedEntry();
-    DCHECK(entry);
-    url = entry->GetURL();
+    // Tests may invoke this function with a null entry, but we don't
+    // want to save zoom levels in this case.
+    if (!entry)
+      return;
+
+    GURL url = entry->GetURL();
     SetZoomLevelForHost(net::GetHostOrSpecFromURL(url), level);
   }
 }
 
 void HostZoomMapImpl::SetZoomLevelForView(int render_process_id,
                                           int render_view_id,
                                           double level,
                                           const std::string& host) {
   if (UsesTemporaryZoomLevel(render_process_id, render_view_id))
     SetTemporaryZoomLevel(render_process_id, render_view_id, level);
@@ skipping 119 matching lines @@
       zoom_level(0.0) {
 }
 
 bool HostZoomMapImpl::TemporaryZoomLevel::operator==(
     const TemporaryZoomLevel& other) const {
   return other.render_process_id == render_process_id &&
          other.render_view_id == render_view_id;
 }
 
 }  // namespace content