Moving gRPC support interfaces out of cronet and into a new component.

components/cronet/ios/cronet_environment.cc

Index: components/cronet/ios/cronet_environment.cc
diff --git a/components/cronet/ios/cronet_environment.cc b/components/cronet/ios/cronet_environment.cc
index cb65294ae6848fb8db178a64976d3afd92faf135..152a1b0f954ecbd172fecfc6c7b60b0987b17891 100644
--- a/components/cronet/ios/cronet_environment.cc
+++ b/components/cronet/ios/cronet_environment.cc
@@ -67,10 +67,6 @@ base::MessageLoop* g_main_message_loop = nullptr;
 
 namespace cronet {
 
-bool CronetEnvironment::IsOnNetworkThread() {
-  return network_io_thread_->task_runner()->BelongsToCurrentThread();
-}
-
 void CronetEnvironment::PostToNetworkThread(
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
@@ -83,8 +79,8 @@ void CronetEnvironment::PostToFileUserBlockingThread(
   file_user_blocking_thread_->task_runner()->PostTask(from_here, task);
 }
 
-net::URLRequestContext* CronetEnvironment::GetURLRequestContext() const {
-  return main_context_.get();
+net::URLRequestContextGetter* CronetEnvironment::GetURLRequestContextGetter() {
+  return request_context_getter_.get();
 }
 
 // static
@@ -223,6 +219,15 @@ void CronetEnvironment::Start() {
   proxy_config_service_ = net::ProxyService::CreateSystemProxyConfigService(
       network_io_thread_->task_runner(), nullptr);
 
+  // Create request_context_getter_ here so that it will be availble as soon

[mef, 2016/10/11 22:09:37]

Would it be easier to have custom net::URLRequestContextGetter which is aware of
CronetEnvironment like in
https://codereview.chromium.org/2146643002/diff/420001/components/cronet/ios/...

[Garrett Casto, 2016/10/12 00:23:36]

Yes. If nothing else this doesn't require getting approval to add
DetachFromThread to URLRequestContext, which seems like a win.

+  // as this function returns. main_context_ won't actually be setup at that
+  // point, but any usage should happen on the network thread and the
+  // initialization callback will be run before any other posted task.
+  main_context_.reset(new net::URLRequestContext);
+  main_context_->DetachFromThread();
+  request_context_getter_ = new net::TrivialURLRequestContextGetter(
+      main_context_.get(), network_io_thread_->task_runner());
+
 #if defined(USE_NSS_CERTS)
   net::SetURLRequestContextForNSSHttpIO(main_context_.get());
 #endif
@@ -243,7 +248,6 @@ void CronetEnvironment::InitializeOnNetworkThread() {
   DCHECK(network_io_thread_->task_runner()->BelongsToCurrentThread());
   base::FeatureList::InitializeInstance(std::string(), std::string());
   // TODO(mef): Use net:UrlRequestContextBuilder instead of manual build.
-  main_context_.reset(new net::URLRequestContext);
   main_context_->set_net_log(net_log_.get());
   std::string user_agent(user_agent_product_name_ +
                          " (iOS); Cronet/" CRONET_VERSION);