[Cronet] Add Hello World response to QuicTestServer and use it in bidirectional stream test.

components/cronet/ios/cronet_bidirectional_stream.cc

Index: components/cronet/ios/cronet_bidirectional_stream.cc
diff --git a/components/cronet/ios/cronet_bidirectional_stream.cc b/components/cronet/ios/cronet_bidirectional_stream.cc
index e229fcd1ec5d34a501a3ff3eb44b07b7bd7aa3f8..c5e091d5c7d2d9f40570ea166dc703b1d43beacd 100644
--- a/components/cronet/ios/cronet_bidirectional_stream.cc
+++ b/components/cronet/ios/cronet_bidirectional_stream.cc
@@ -208,7 +208,9 @@ void CronetBidirectionalStream::ReadDataOnNetworkThread(
   DCHECK(!read_buffer_);
   if (read_state_ != WAITING_FOR_READ) {
     DLOG(ERROR) << "Unexpected Read Data in read_state " << WAITING_FOR_READ;
-    OnFailed(net::ERR_UNEXPECTED);
+    // Invoke OnFailed unless it is already invoked.
+    if (read_state_ != ERROR)
+      OnFailed(net::ERR_UNEXPECTED);
     return;
   }
   read_state_ = READING;
@@ -235,7 +237,9 @@ void CronetBidirectionalStream::WriteDataOnNetworkThread(
   DCHECK(!write_buffer_);
   if (write_state_ != WAITING_FOR_WRITE) {
     DLOG(ERROR) << "Unexpected Write Data in write_state " << write_state_;
-    OnFailed(net::ERR_UNEXPECTED);
+    // Invoke OnFailed unless it is already invoked.
+    if (write_state_ != ERROR)
+      OnFailed(net::ERR_UNEXPECTED);

[xunjieli, 2016/04/28 15:23:33]

If the request has been canceled, we probably could provide ERR_ABORTED as the
better error code.

[mef, 2016/04/28 17:11:26]

That's an interesting point. I think we shouldn't invoke OnFailed at all if
stream is in one one of the terminal states (DONE, CANCELED or FAILED). WDYT?

[xunjieli, 2016/04/28 20:20:45]

I am not sure. Either approach is fine with me as long as we document it in the
API doc and be consistent. We can handle this in a follow-up, since I guess we
will end up changing the API anyway to handle flush.

     return;
   }
   write_state_ = WRITING;