Add pause/resume functionality to precache

components/precache/content/precache_manager.cc

Index: components/precache/content/precache_manager.cc
diff --git a/components/precache/content/precache_manager.cc b/components/precache/content/precache_manager.cc
index 1d2ddb653b7742cb2d7257d3ea1aeaa37f5aba25..d69309929e47e2da18ea4caaefee6240e5468946 100644
--- a/components/precache/content/precache_manager.cc
+++ b/components/precache/content/precache_manager.cc
@@ -167,7 +167,14 @@ void PrecacheManager::CancelPrecaching() {
     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();
 
@@ -250,7 +257,6 @@ void PrecacheManager::Shutdown() {
 
 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
@@ -278,7 +284,6 @@ void PrecacheManager::OnHostsReceived(
   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,
@@ -288,7 +293,13 @@ void PrecacheManager::OnHostsReceived(
           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();
 }