Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/prerendering_loader.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_
 
 #include <memory>
+#include <string>
+#include <vector>
 
 #include "base/callback.h"
 #include "chrome/browser/android/offline_pages/prerender_adapter.h"
 #include "components/offline_pages/core/background/offliner.h"
 #include "components/offline_pages/core/snapshot_controller.h"
 
 class GURL;
 
 namespace content {
 class BrowserContext;
@@ skipping 78 matching lines @@
   void HandleLoadEvent();
 
   // Handles some event/signal that loading has stopped (whether due to a
   // failure, cancel, or stop request). It may be due to some asynchronous
   // trigger that occurs after the request has stopped for some other reason.
   void HandleLoadingStopped();
 
   // Cancels any current prerender and moves loader to idle state.
   void CancelPrerender();
 
+  // Returns a vector of strings for analysis of loading progress.
+  const std::vector<std::string>& GetLoadingSignalData() {
+    return signal_data_;
+  }
+
   // Tracks loading state including whether the Loader is idle.
   State state_;
 
   // Handles determining when to report page is LOADED.
   std::unique_ptr<SnapshotController> snapshot_controller_;
 
   // Not owned.
   content::BrowserContext* browser_context_;
 
   // Adapter for handling calls to the prerender stack.
   std::unique_ptr<PrerenderAdapter> adapter_;
 
   // A WebContents for the active load request that is used to hold the session
   // storage namespace for rendering. This will NOT have the loaded page.
   std::unique_ptr<content::WebContents> session_contents_;
 
+  // Signal data collected for this rendering attempt
+  std::vector<std::string> signal_data_;
+
   // Callback to call when the active load request completes, fails, or is
   // canceled.
   LoadPageCallback load_done_callback_;
 
   // Callback to call when we know more bytes have loaded from the network.
   ProgressCallback progress_callback_;
 
   // True if the lowbar of snapshotting a page is met.
   bool is_lowbar_met_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderingLoader);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_