Fix an issue that PrerenderLoader::OnPrerenderStart() never gets called.

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 40 matching lines @@
   bool accepted = adapter_->StartPrerender(
       browser_context_, url, sessionStorageNamespace, renderWindowSize);
   if (!accepted)
     return false;
 
   DCHECK(adapter_->IsActive());
   snapshot_controller_.reset(
       new SnapshotController(base::ThreadTaskRunnerHandle::Get(), this));
   callback_ = callback;
   session_contents_.swap(new_web_contents);
-  state_ = State::PENDING;
+  state_ = State::LOADING;
   return true;
 }
 
 void PrerenderingLoader::StopLoading() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   CancelPrerender();
 }
 
 bool PrerenderingLoader::CanPrerender() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   return adapter_->CanPrerender();
 }
 
 bool PrerenderingLoader::IsIdle() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   return state_ == State::IDLE;
 }
 
 bool PrerenderingLoader::IsLoaded() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   return state_ == State::LOADED;
 }
 
 void PrerenderingLoader::SetAdapterForTesting(
     std::unique_ptr<PrerenderAdapter> prerender_adapter) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   adapter_ = std::move(prerender_adapter);
 }
 
-void PrerenderingLoader::OnPrerenderStart() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  DCHECK(state_ == State::PENDING);
-  state_ = State::LOADING;
-}
-
 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();
 }
 
 void PrerenderingLoader::OnPrerenderDomContentLoaded() {
@@ skipping 92 matching lines @@
 void PrerenderingLoader::CancelPrerender() {
   if (adapter_->IsActive()) {
     adapter_->DestroyActive();
   }
   snapshot_controller_.reset(nullptr);
   session_contents_.reset(nullptr);
   state_ = State::IDLE;
 }
 
 }  // namespace offline_pages