[Offline pages] Stop observing web contents and reset to null after use. Only create a new web cont…

chrome/browser/android/offline_pages/background_loader_offliner.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/background_loader_offliner.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/sys_info.h"
 #include "chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h"
 #include "chrome/browser/android/offline_pages/offliner_helper.h"
@@ skipping 131 matching lines @@
         static_cast<int>(OfflinePagesCctApiPrerenderAllowedStatus::
                              NETWORK_PREDICTION_DISABLED) +
             1);
   }
 
   if (!OfflinePageModel::CanSaveURL(request.url())) {
     DVLOG(1) << "Not able to save page for requested url: " << request.url();
     return false;
   }
 
-  if (!loader_)
-    ResetState();
+  ResetLoader();
+  AttachObservers();
 
   // Track copy of pending request.
   pending_request_.reset(new SavePageRequest(request));
   completion_callback_ = completion_callback;
   progress_callback_ = progress_callback;
 
   // Listen for app foreground/background change.
   app_listener_.reset(new base::android::ApplicationStatusListener(
       base::Bind(&BackgroundLoaderOffliner::OnApplicationStateChange,
                  weak_ptr_factory_.GetWeakPtr())));
@@ skipping 184 matching lines @@
     save_status = RequestStatus::SAVE_FAILED;
 
   completion_callback_.Run(request, save_status);
 }
 
 void BackgroundLoaderOffliner::ResetState() {
   pending_request_.reset();
   snapshot_controller_.reset();
   page_load_state_ = SUCCESS;
   network_bytes_ = 0LL;
-  // TODO(chili): Remove after RequestCoordinator can handle multiple offliners.
-  // We reset the loader and observer after completion so loaders
-  // will not be re-used across different requests/tries. This is a temporary
-  // solution while there exists assumptions about the number of offliners
-  // there are.
+  content::WebContentsObserver::Observe(nullptr);
+  loader_.reset();
+}
+
+void BackgroundLoaderOffliner::ResetLoader() {
   loader_.reset(
       new background_loader::BackgroundLoaderContents(browser_context_));
+}
+
+void BackgroundLoaderOffliner::AttachObservers() {
   content::WebContents* contents = loader_->web_contents();
   content::WebContentsObserver::Observe(contents);
   OfflinerData::AddToWebContents(contents, this);
 }
 
 void BackgroundLoaderOffliner::OnApplicationStateChange(
     base::android::ApplicationState application_state) {
   if (pending_request_ && is_low_end_device_ &&
       application_state ==
           base::android::APPLICATION_STATE_HAS_RUNNING_ACTIVITIES) {
@@ skipping 12 matching lines @@
     int64_t offline_id) {
   // If for some reason the request was reset during while waiting for callback
   // ignore the completion callback.
   if (pending_request_ && pending_request_->request_id() != offline_id)
     return;
   completion_callback_.Run(request, RequestStatus::FOREGROUND_CANCELED);
 }
 }  // namespace offline_pages
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(offline_pages::OfflinerData);