Check if there is a SW controlling the start page for app banner.

chrome/browser/android/banners/app_banner_manager.h

Index: chrome/browser/android/banners/app_banner_manager.h
diff --git a/chrome/browser/android/banners/app_banner_manager.h b/chrome/browser/android/banners/app_banner_manager.h
index c65d1479a5e62c29b3fe2019f5a223e7cdda43ec..a225ea8a4e29d2f7e0a3adb4f2517ab22bb799f8 100644
--- a/chrome/browser/android/banners/app_banner_manager.h
+++ b/chrome/browser/android/banners/app_banner_manager.h
@@ -7,7 +7,9 @@
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_weak_ref.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/android/banners/app_banner_infobar_delegate.h"
 #include "chrome/browser/bitmap_fetcher/bitmap_fetcher.h"
 #include "content/public/browser/web_contents_observer.h"
@@ -109,6 +111,8 @@ class AppBannerManager : public chrome::BitmapFetcherDelegate,
   virtual gfx::Image GetIcon() const override;
 
  private:
+  class IOThreadHandler;
+
   // Gets the preferred icon size for the banner icons.
   int GetPreferredIconSize();
 
@@ -125,6 +129,10 @@ class AppBannerManager : public chrome::BitmapFetcherDelegate,
                                    const std::string& tag_content,
                                    const GURL& expected_url);
 
+  // Called when the result of the CheckHasSameServiceWorker query has
+  // completed.
+  void OnDidCheckHasSameServiceWorker(bool has_same);
+
   // Fetches the icon for an app.
   scoped_ptr<chrome::BitmapFetcher> fetcher_;
   GURL validated_url_;
@@ -134,6 +142,15 @@ class AppBannerManager : public chrome::BitmapFetcherDelegate,
   // AppBannerManager on the Java side.
   JavaObjectWeakGlobalRef weak_java_banner_view_manager_;
 
+  // Object to handle responses that are returned on the IO thread.
+  scoped_refptr<IOThreadHandler> io_thread_handler_;
+
+  // A weak pointer is used as the lifetime of the ServiceWorkerContext is
+  // longer than the lifetime of this banner manager. The banner manager
+  // may be destroyed when calls sent to the ServiceWorkerContext are
+  // completed.

[gone, 2015/02/04 17:28:01]

What does "may" mean in this context? Might be destroyed, or is allowed to be
destroyed? I'm wary of the former, because the Java-side AppBannerManager is
supposed to own the native AppBannerManager, but I'm guessing it's the latter.

[benwells, 2015/02/04 17:35:36]

It means 'might'. The ServiceWorkerContext is owned by the storage partition,
which is owned by the profile. The banner manager is (I think) owned by the tab.
So if the banner manager starts a call, then the tab is closed before the call
is completed, it could be gone.

This case should be handled through the combination of the web pointer and the
IOThread handler.

[gone, 2015/02/04 17:40:10]

Ah, alright. As long as the ownership is being tracked properly then this should
be fine.  Can you flip that "may be destroyed" to "might be gone" for clarity?

+  base::WeakPtrFactory<AppBannerManager> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(AppBannerManager);
 };  // class AppBannerManager