Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/prerendering_loader.cc

 // 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.
 
 #include "chrome/browser/android/offline_pages/prerendering_loader.h"
 
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 134 matching lines @@
   adapter_ = std::move(prerender_adapter);
 }
 
 void PrerenderingLoader::OnPrerenderStopLoading() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!IsIdle());
   DCHECK(adapter_->GetWebContents());
   // Inform SnapshotController of OnLoad event so it can determine
   // when to consider it really LOADED.
   snapshot_controller_->DocumentOnLoadCompletedInMainFrame();
+
+  // Add this signal to signal_data_.
+  signal_data_.push_back(std::string("OnLoad signal seen"));
 }
 
 void PrerenderingLoader::OnPrerenderDomContentLoaded() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!IsIdle());
   if (!adapter_->GetWebContents()) {
     // Without a WebContents object at this point, we are done.
     HandleLoadingStopped();
   } else {
     is_lowbar_met_ = true;
     if (kConsiderDclForSnapshot) {
       // Inform SnapshotController of DomContentLoaded event so it can
       // determine when to consider it really LOADED (e.g., some multiple
       // second delay from this event).
       snapshot_controller_->DocumentAvailableInMainFrame();
     }
+
+    // Add this signal to signal_data_.
+    signal_data_.push_back(std::string("Dom Content Loaded signal seen"));
   }
 }
 
 void PrerenderingLoader::OnPrerenderStop() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   HandleLoadingStopped();
 }
 
 void PrerenderingLoader::OnPrerenderNetworkBytesChanged(int64_t bytes) {
   if (state_ == State::LOADING)
@@ skipping 87 matching lines @@
   if (adapter_->IsActive()) {
     adapter_->DestroyActive();
   }
   snapshot_controller_.reset(nullptr);
   session_contents_.reset(nullptr);
   state_ = State::IDLE;
   is_lowbar_met_ = false;
 }
 
 }  // namespace offline_pages