Use per-frame TaskRunner instead of thread's default in DataConsumerHandle

content/child/shared_memory_data_consumer_handle.h

Index: content/child/shared_memory_data_consumer_handle.h
diff --git a/content/child/shared_memory_data_consumer_handle.h b/content/child/shared_memory_data_consumer_handle.h
index 0a98b760aa7d492b4bce56346173ec25dbed55a4..b64ad2b7d37aedbd4279923c713f9e7b447ee209 100644
--- a/content/child/shared_memory_data_consumer_handle.h
+++ b/content/child/shared_memory_data_consumer_handle.h
@@ -16,6 +16,10 @@
 #include "content/public/child/request_peer.h"
 #include "third_party/WebKit/public/platform/WebDataConsumerHandle.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace content {
 
 // This class is a WebDataConsumerHandle that accepts RequestPeer::ReceivedData.
@@ -50,7 +54,8 @@ class CONTENT_EXPORT SharedMemoryDataConsumerHandle final
 
   class ReaderImpl final : public Reader {
    public:
-    ReaderImpl(scoped_refptr<Context> context, Client* client);
+    ReaderImpl(scoped_refptr<Context> context, Client* client,
+               scoped_refptr<base::SingleThreadTaskRunner> reader_task_runner);
     ~ReaderImpl() override;
     Result read(void* data,
                 size_t size,
@@ -81,7 +86,11 @@ class CONTENT_EXPORT SharedMemoryDataConsumerHandle final
                                  std::unique_ptr<Writer>* writer);
   ~SharedMemoryDataConsumerHandle() override;
 
-  std::unique_ptr<Reader> obtainReader(Client* client) override;
+  // Unlike to other Reader, |reader_task_runner| here is nullable, so that
+  // the test code don't need to create blink::WebTaskRunner.
+  std::unique_ptr<Reader> obtainReader(
+      Client* client,
+      std::unique_ptr<blink::WebTaskRunner> reader_task_runner) override;
 
  private:
   const char* debugName() const override;