Teach mojo::Watcher in URLResponseBodyConsumer the correct task runner

This CL makes mojo::Watcher run on the correct task runner instead of the
default task runner of the main thread.

BUG=603396

Review-Url: https://codereview.chromium.org/2274833002
Cr-Commit-Position: refs/heads/master@{#415537}

content/child/resource_dispatcher.cc

@@ -98,7 +98,7 @@ class URLLoaderClientImpl final : public mojom::URLLoaderClient {
       mojo::ScopedDataPipeConsumerHandle body) override {
     DCHECK(!body_consumer_);
     body_consumer_ = new URLResponseBodyConsumer(
-        request_id_, resource_dispatcher_, std::move(body), task_runner_.get());
+        request_id_, resource_dispatcher_, std::move(body), task_runner_);
   }
 
   void OnComplete(const ResourceRequestCompletionStatus& status) override {

content/child/url_response_body_consumer.cc

@@ -44,10 +44,11 @@ URLResponseBodyConsumer::URLResponseBodyConsumer(
     int request_id,
     ResourceDispatcher* resource_dispatcher,
     mojo::ScopedDataPipeConsumerHandle handle,
-    base::SingleThreadTaskRunner* task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : request_id_(request_id),
       resource_dispatcher_(resource_dispatcher),
       handle_(std::move(handle)),
+      handle_watcher_(task_runner),
       has_seen_end_of_data_(!handle_.is_valid()) {
   handle_watcher_.Start(
       handle_.get(), MOJO_HANDLE_SIGNAL_READABLE,
@@ -83,7 +84,6 @@ void URLResponseBodyConsumer::OnReadable(MojoResult unused) {
     return;
 
   // TODO(yhirano): Suppress notification when deferred.
-  // TODO(yhirano): Run this operation on the loading task runner.
   while (!has_been_cancelled_) {
     const void* buffer = nullptr;
     uint32_t available = 0;

content/child/url_response_body_consumer.h

@@ -31,10 +31,11 @@ class CONTENT_EXPORT URLResponseBodyConsumer final
     : public base::RefCounted<URLResponseBodyConsumer>,
       public base::SupportsWeakPtr<URLResponseBodyConsumer> {
  public:
-  URLResponseBodyConsumer(int request_id,
-                          ResourceDispatcher* resource_dispatcher,
-                          mojo::ScopedDataPipeConsumerHandle handle,
-                          base::SingleThreadTaskRunner* task_runner);
+  URLResponseBodyConsumer(
+      int request_id,
+      ResourceDispatcher* resource_dispatcher,
+      mojo::ScopedDataPipeConsumerHandle handle,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
 
   // Sets the completion status. The completion status is dispatched to the
   // ResourceDispatcher when the both following conditions hold:

content/child/url_response_body_consumer_unittest.cc

@@ -135,7 +135,7 @@ TEST_F(URLResponseBodyConsumerTest, ReceiveData) {
 
   scoped_refptr<URLResponseBodyConsumer> consumer(new URLResponseBodyConsumer(
       request_id, dispatcher_.get(), std::move(data_pipe.consumer_handle),
-      message_loop_.task_runner().get()));
+      message_loop_.task_runner()));
 
   mojo::ScopedDataPipeProducerHandle writer =
       std::move(data_pipe.producer_handle);
@@ -160,7 +160,7 @@ TEST_F(URLResponseBodyConsumerTest, OnCompleteThenClose) {
 
   scoped_refptr<URLResponseBodyConsumer> consumer(new URLResponseBodyConsumer(
       request_id, dispatcher_.get(), std::move(data_pipe.consumer_handle),
-      message_loop_.task_runner().get()));
+      message_loop_.task_runner()));
 
   consumer->OnComplete(ResourceRequestCompletionStatus());
   mojo::ScopedDataPipeProducerHandle writer =
@@ -192,7 +192,7 @@ TEST_F(URLResponseBodyConsumerTest, CloseThenOnComplete) {
 
   scoped_refptr<URLResponseBodyConsumer> consumer(new URLResponseBodyConsumer(
       request_id, dispatcher_.get(), std::move(data_pipe.consumer_handle),
-      message_loop_.task_runner().get()));
+      message_loop_.task_runner()));
 
   ResourceRequestCompletionStatus status;
   status.error_code = net::ERR_FAILED;