Keep the app list start page isolated from the browser's default zoom.

chrome/browser/ui/app_list/start_page_service.h

Index: chrome/browser/ui/app_list/start_page_service.h
diff --git a/chrome/browser/ui/app_list/start_page_service.h b/chrome/browser/ui/app_list/start_page_service.h
index 3c56030be3f11f9df5444adb2afeb19212d1d0fb..3792b6da64dc016c314a98874cfda0499cb4d443 100644
--- a/chrome/browser/ui/app_list/start_page_service.h
+++ b/chrome/browser/ui/app_list/start_page_service.h
@@ -20,9 +20,12 @@
 #include "chrome/browser/ui/app_list/speech_recognizer_delegate.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_observer.h"
 #include "ui/app_list/speech_ui_model_observer.h"
 
 namespace content {
+struct FrameNavigateParams;
+struct LoadCommittedDetails;
 struct SpeechRecognitionSessionPreamble;
 }
 
@@ -42,6 +45,7 @@ class StartPageObserver;
 // StartPageService collects data to be displayed in app list's start page
 // and hosts the start page contents.
 class StartPageService : public KeyedService,
+                         public content::WebContentsObserver,
                          public SpeechRecognizerDelegate {
  public:
   typedef std::vector<scoped_refptr<const extensions::Extension> >
@@ -113,6 +117,11 @@ class StartPageService : public KeyedService,
   // KeyedService overrides:
   void Shutdown() override;
 
+  // contents::WebContentsObserver overrides;
+  void DidNavigateMainFrame(
+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) override;
+
   // Change the known microphone availability. |available| should be true if
   // the microphone exists and is available for use.
   void OnMicrophoneChanged(bool available);