Add support for fallback content for the frame. This includes main and subframes.

content/browser/appcache/appcache_url_loader_job.h

Index: content/browser/appcache/appcache_url_loader_job.h
diff --git a/content/browser/appcache/appcache_url_loader_job.h b/content/browser/appcache/appcache_url_loader_job.h
index 8cd759ed453ca085e109421826162b766f3a553f..2ac26ba2e97f347fdf9f488b9a9f2a63efd2c365 100644
--- a/content/browser/appcache/appcache_url_loader_job.h
+++ b/content/browser/appcache/appcache_url_loader_job.h
@@ -96,6 +96,10 @@ class CONTENT_EXPORT AppCacheURLLoaderJob : public AppCacheJob,
     main_resource_loader_callback_ = std::move(callback);
   }
 
+  void set_main_resource_fallback_handler(ResponseFallback fallback_handler) {
+    main_resource_fallback_handler_ = std::move(fallback_handler);
+  }
+
   // Subresource request load information is passed in the
   // |subresource_load_info| parameter. This includes the request id, the
   // client pointer, etc.
@@ -111,6 +115,13 @@ class CONTENT_EXPORT AppCacheURLLoaderJob : public AppCacheJob,
     sub_resource_handler_ = std::move(handler);
   }
 
+  // Binds to the URLLoaderRequest instance passed in the |request| parameter.
+  // The URLLoaderClient instance is passed in the |client| parameter. This
+  // enables the client to receive notifications/data, etc for the ensuing
+  // URL load.
+  void BindRequest(mojom::URLLoaderClientPtr client,
+                   mojom::URLLoaderRequest request);
+
  protected:
   // AppCacheJob::Create() creates this instance.
   friend class AppCacheJob;
@@ -206,6 +217,10 @@ class CONTENT_EXPORT AppCacheURLLoaderJob : public AppCacheJob,
   // info when we receive it.
   AppCacheURLLoaderRequest* appcache_request_;
 
+  // Contains the fallback response handler for the main resource, which is
+  // invoked by the client to request fallback responses.
+  ResponseFallback main_resource_fallback_handler_;
+
   DISALLOW_COPY_AND_ASSIGN(AppCacheURLLoaderJob);
 };