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

chrome/browser/ui/panels/panel_host.cc

Index: chrome/browser/ui/panels/panel_host.cc
diff --git a/chrome/browser/ui/panels/panel_host.cc b/chrome/browser/ui/panels/panel_host.cc
index 670ae731fc4749e4ec88b0c47d1073fa1ee294a3..907b11a08501207df4812b0ba7d7f692b7b5ccb6 100644
--- a/chrome/browser/ui/panels/panel_host.cc
+++ b/chrome/browser/ui/panels/panel_host.cc
@@ -17,6 +17,7 @@
 #include "chrome/browser/ui/browser_navigator.h"
 #include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/prefs/prefs_tab_helper.h"
+#include "chrome/browser/ui/zoom/zoom_controller.h"
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/notification_service.h"
@@ -54,6 +55,9 @@ void PanelHost::Init(const GURL& url) {
   web_contents_.reset(content::WebContents::Create(create_params));
   extensions::SetViewType(web_contents_.get(), extensions::VIEW_TYPE_PANEL);
   web_contents_->SetDelegate(this);
+  // web_contents_ may be passed to chrome_page_zoom::Zoom(), so it needs
+  // a ZoomController.
+  ZoomController::CreateForWebContents(web_contents_.get());
   content::WebContentsObserver::Observe(web_contents_.get());
 
   // Needed to give the web contents a Tab ID. Extension APIs