Use heuristic to work out when to prompt for app install banners.

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 263704d59a26ac685a4d1564c0a078d6d9863cc7..eee1536de1a294638fa2ef591698da61ec527ec3 100644
--- a/chrome/browser/android/banners/app_banner_manager.h
+++ b/chrome/browser/android/banners/app_banner_manager.h
@@ -130,6 +130,9 @@ class AppBannerManager : public chrome::BitmapFetcherDelegate,
   // Called when the result of the CheckHasServiceWorker query has completed.
   void OnDidCheckHasServiceWorker(bool has_same);
 
+  // Update the record of banner events and check if the banner should be shown.
+  bool CheckIfShouldShow(const std::string& package_or_start_url);
+
   // Fetches the icon for an app.
   scoped_ptr<chrome::BitmapFetcher> fetcher_;
   GURL validated_url_;