[Extensions] Add perf metrics for StartRequest()/HandleResponse()

extensions/renderer/send_request_natives.cc

 // Copyright 2014 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 "extensions/renderer/send_request_natives.h"
 
 #include <stdint.h>
 
 #include "base/json/json_reader.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/timer/elapsed_timer.h"
 #include "content/public/child/v8_value_converter.h"
 #include "extensions/renderer/request_sender.h"
 #include "extensions/renderer/script_context.h"
 
 using content::V8ValueConverter;
 
 namespace extensions {
 
 SendRequestNatives::SendRequestNatives(RequestSender* request_sender,
                                        ScriptContext* context)
     : ObjectBackedNativeHandler(context), request_sender_(request_sender) {
   RouteFunction(
       "StartRequest",
       base::Bind(&SendRequestNatives::StartRequest, base::Unretained(this)));
   RouteFunction(
       "GetGlobal",
       base::Bind(&SendRequestNatives::GetGlobal, base::Unretained(this)));
 }
 
 // Starts an API request to the browser, with an optional callback.  The
 // callback will be dispatched to EventBindings::HandleResponse.
 void SendRequestNatives::StartRequest(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
+  base::ElapsedTimer timer;
   CHECK_EQ(5, args.Length());
   std::string name = *v8::String::Utf8Value(args[0]);
   bool has_callback = args[2]->BooleanValue();
   bool for_io_thread = args[3]->BooleanValue();
   bool preserve_null_in_objects = args[4]->BooleanValue();
 
   int request_id = request_sender_->GetNextRequestId();
   args.GetReturnValue().Set(static_cast<int32_t>(request_id));
 
   std::unique_ptr<V8ValueConverter> converter(V8ValueConverter::create());
 
   // See http://crbug.com/149880. The context menus APIs relies on this, but
   // we shouldn't really be doing it (e.g. for the sake of the storage API).
   converter->SetFunctionAllowed(true);
 
   if (!preserve_null_in_objects)
     converter->SetStripNullFromObjects(true);
 
   std::unique_ptr<base::Value> value_args(
       converter->FromV8Value(args[1], context()->v8_context()));
   if (!value_args.get() || !value_args->IsType(base::Value::TYPE_LIST)) {
     NOTREACHED() << "Unable to convert args passed to StartRequest";
     return;
   }
 
-  request_sender_->StartRequest(
-      context(),
-      name,
-      request_id,
-      has_callback,
-      for_io_thread,
-      static_cast<base::ListValue*>(value_args.get()));
+  if (request_sender_->StartRequest(
+          context(),
+          name,
+          request_id,
+          has_callback,
+          for_io_thread,
+          static_cast<base::ListValue*>(value_args.get()))) {
+    // TODO(devlin): Would it be useful to partition this data based on
+    // extension function once we have a suitable baseline? crbug.com/608561.
+    UMA_HISTOGRAM_TIMES("Extensions.Functions.StartRequestElapsedTime",
+                        timer.Elapsed());
+  }
 }
 
 void SendRequestNatives::GetGlobal(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   CHECK_EQ(1, args.Length());
   CHECK(args[0]->IsObject());
   v8::Local<v8::Context> v8_context =
       v8::Local<v8::Object>::Cast(args[0])->CreationContext();
   if (ContextCanAccessObject(context()->v8_context(), v8_context->Global(),
                              false)) {
     args.GetReturnValue().Set(v8_context->Global());
   }
 }
 
 }  // namespace extensions