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 c333bcb555399187596406be0486df00bb227771..b82ec7afe3273b6cfdf0fa6ad18eddb4559b5c39 100644
--- a/chrome/browser/android/banners/app_banner_manager.h
+++ b/chrome/browser/android/banners/app_banner_manager.h
@@ -138,6 +138,13 @@ class AppBannerManager : public chrome::BitmapFetcherDelegate,
   // Called when the result of the CheckHasServiceWorker query has completed.
   void OnDidCheckHasServiceWorker(bool has_service_worker);
 
+  // Record that the banner could be shown at this point, if the triggering
+  // heuristic allowed.
+  void RecordCouldShowBanner(const std::string& package_or_start_url);
+
+  // 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_;