Add pause/resume functionality to precache

components/precache/content/precache_manager.cc

 // Copyright 2013 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 "components/precache/content/precache_manager.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 149 matching lines @@
 }
 
 void PrecacheManager::CancelPrecaching() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   if (!is_precaching_) {
     // Do nothing if precaching is not in progress.
     return;
   }
   is_precaching_ = false;
+  // If cancellation occurs after StartPrecaching but before OnHostsReceived,
+  // is_precaching will be true, but the precache_fetcher_ will not yet be
+  // constructed.
+  if (precache_fetcher_)
+    precache_fetcher_->Shutdown();
+}
 
+void PrecacheManager::OnShutdownDone() {
   // Destroying the |precache_fetcher_| will cancel any fetch in progress.
   precache_fetcher_.reset();
 
   // Uninitialize the callback so that any scoped_refptrs in it are released.
   precache_completion_callback_.Reset();
 }
 
 bool PrecacheManager::IsPrecaching() const {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   return is_precaching_;
@@ skipping 62 matching lines @@
       base::Bind(&PrecacheDatabase::ClearHistory,
                  base::Unretained(precache_database_.get())));
 }
 
 void PrecacheManager::Shutdown() {
   CancelPrecaching();
 }
 
 void PrecacheManager::OnDone() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-
   precache_fetcher_.reset();
 
   // Run completion callback if not null. It's null if the client is in the
   // Control group and CancelPrecaching is called before TopHosts computation
   // finishes.
   if (!precache_completion_callback_.is_null()) {
     precache_completion_callback_.Run(!is_precaching_);
     // Uninitialize the callback so that any scoped_refptrs in it are released.
     precache_completion_callback_.Reset();
   }
 
   is_precaching_ = false;
 }
 
 void PrecacheManager::OnHostsReceived(
     const history::TopHostsList& host_counts) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   if (!is_precaching_) {
     // Don't start precaching if it was canceled while waiting for the list of
     // hosts.
     return;
   }
 
   std::vector<std::string> hosts;
   for (const auto& host_count : host_counts)
     hosts.push_back(host_count.first);
-
   // Start precaching.
   precache_fetcher_.reset(new PrecacheFetcher(
       hosts,
       content::BrowserContext::GetDefaultStoragePartition(browser_context_)->
             GetURLRequestContext(),
       GURL(variations::GetVariationParamValue(
           kPrecacheFieldTrialName, kConfigURLParam)),
       variations::GetVariationParamValue(
           kPrecacheFieldTrialName, kManifestURLPrefixParam),
-      this));
+      this,
+      precache_database_->GetWeakPtr(),
+      BrowserThread::GetMessageLoopProxyForThread( BrowserThread::DB)));
+  precache_fetcher_->Init(base::TimeDelta::FromHours(6));
+}
+
+void PrecacheManager::OnInitDone() {

[sclittle, 2016/05/10 00:01:26]

Why is this method necessary? Couldn't PrecacheFetcher::Init be combined with
PrecacheFetcher::Start?

[bengr, 2016/05/19 01:25:44]

Done.

   precache_fetcher_->Start();
 }
 
 void PrecacheManager::OnHostsReceivedThenDone(
     const history::TopHostsList& host_counts) {
   OnDone();
 }
 
 }  // namespace precache