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

chrome/browser/devtools/devtools_window.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/devtools/devtools_window.h"
 
 #include <algorithm>
 
 #include "base/json/json_reader.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/scoped_user_pref_update.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_page_zoom.h"
 #include "chrome/browser/file_select_helper.h"
 #include "chrome/browser/infobars/infobar_service.h"
 #include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #include "chrome/browser/ui/browser_iterator.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/host_desktop.h"
 #include "chrome/browser/ui/prefs/prefs_tab_helper.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/webui/devtools_ui.h"
+#include "chrome/browser/ui/zoom/zoom_controller.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/url_constants.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/native_web_keyboard_event.h"
@@ skipping 668 matching lines @@
       ignore_set_is_docked_(false),
       intercepted_page_beforeunload_(false) {
   // Set up delegate, so we get fully-functional window immediately.
   // It will not appear in UI though until |load_state_ == kLoadCompleted|.
   main_web_contents_->SetDelegate(this);
   bindings_ = new DevToolsUIBindings(
       main_web_contents_,
       DevToolsUIBindings::ApplyThemeToURL(profile, url));
   // Bindings take ownership over devtools as its delegate.
   bindings_->SetDelegate(this);
+  // DevTools uses chrome_page_zoom::Zoom(), so main_web_contents_ requires a
+  // ZoomController.
+  ZoomController::CreateForWebContents(main_web_contents_);
 
   g_instances.Get().push_back(this);
 
   // There is no inspected_rvh in case of shared workers.
   if (inspected_rvh)
     inspected_contents_observer_.reset(new ObserverWithAccessor(
         content::WebContents::FromRenderViewHost(inspected_rvh)));
   event_forwarder_.reset(new DevToolsEventForwarder(this));
 }
 
@@ skipping 543 matching lines @@
       closure.Run();
     return;
   }
   load_completed_callback_ = closure;
 }
 
 bool DevToolsWindow::ForwardKeyboardEvent(
     const content::NativeWebKeyboardEvent& event) {
   return event_forwarder_->ForwardEvent(event);
 }