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

components/cronet/ios/cronet_environment.h

Index: components/cronet/ios/cronet_environment.h
diff --git a/components/cronet/ios/cronet_environment.h b/components/cronet/ios/cronet_environment.h
index 30f29ea2c9f4ee3ebde133a822fc226e0a79a247..5772bef42f36b0f438a2e21c3ac01d75f76b8761 100644
--- a/components/cronet/ios/cronet_environment.h
+++ b/components/cronet/ios/cronet_environment.h
@@ -13,6 +13,7 @@
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
 #include "components/cronet/url_request_context_config.h"
+#include "components/grpc_support/environment.h"
 #include "net/cert/cert_verifier.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_context.h"
@@ -34,7 +35,7 @@ class WriteToFileNetLogObserver;
 namespace cronet {
 // CronetEnvironment contains all the network stack configuration
 // and initialization.
-class CronetEnvironment {
+class CronetEnvironment : public grpc_support::Environment {
  public:
   // Initialize Cronet environment globals. Must be called only once on the
   // main thread.
@@ -47,9 +48,6 @@ class CronetEnvironment {
   // Starts this instance of Cronet environment.
   void Start();
 
-  // The full user-agent.
-  std::string user_agent();
-
   // Creates a new net log (overwrites existing file with this name). If
   // actively logging, this call is ignored.
   void StartNetLog(base::FilePath::StringType file_name, bool log_bytes);
@@ -80,13 +78,12 @@ class CronetEnvironment {
     ssl_key_log_file_name_ = ssl_key_log_file_name;
   }
 
-  net::URLRequestContext* GetURLRequestContext() const;
-
-  bool IsOnNetworkThread();
-
-  // Runs a closure on the network thread.
+  // grpc_support::Environment implementation.
+  bool IsOnNetworkThread() override;
   void PostToNetworkThread(const tracked_objects::Location& from_here,
-                           const base::Closure& task);
+                           const base::Closure& task) override;
+  net::URLRequestContext* GetURLRequestContext() const override;
+  std::string UserAgent() override;
 
  private:
   // Performs initialization tasks that must happen on the network thread.