getUserMeida: report device starting states

content/browser/renderer_host/media/video_capture_controller.cc

 // Copyright (c) 2012 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 "content/browser/renderer_host/media/video_capture_controller.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
@@ skipping 453 matching lines @@
       continue;
     client->event_handler->OnError(client->controller_id);
   }
 }
 
 void VideoCaptureController::OnLog(const std::string& message) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   MediaStreamManager::SendMessageToNativeLog("Video capture: " + message);
 }
 
+void VideoCaptureController::OnStarted() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  state_ = VIDEO_CAPTURE_STATE_STARTED;

[chfremer, 2017/02/22 19:13:58]

Why are we setting this here?

Looking at the usages of |state_|, it only ever takes one of two possible
values, VIDEO_CAPTURE_STATE_STARTED and VIDEO_CAPTURE_STATE_ERROR. This means,
what this really is is just a flag indicating whether or not OnError() was
received (I would actually recommend changinge |state_| to a boolean and naming
it |error_flag_| or |is_in_error_state_|). 

Before this CL, it looks like there was not way to change back from
VIDEO_CAPTURE_STATE_ERROR to VIDEO_CAPTURE_STATE_STARTED, and I don't see why we
would intend to change this here. The only way to recover from an error state is
to discard and re-create the device.

[braveyao, 2017/02/23 00:06:25]

Done.
You're right. No need here.

+
+  for (const auto& client : controller_clients_) {
+    if (client->session_closed)
+      continue;
+    client->event_handler->OnStarted(client->controller_id);
+  }
+}
+
 void VideoCaptureController::OnBufferRetired(int buffer_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   auto buffer_context_iter = FindUnretiredBufferContextFromBufferId(buffer_id);
   DCHECK(buffer_context_iter != buffer_contexts_.end());
 
   // If there are any clients still using the buffer, we need to allow them
   // to finish up. We need to hold on to the BufferContext entry until then,
   // because it contains the consumer hold.
   if (buffer_context_iter->HasZeroConsumerHoldCount())
@@ skipping 68 matching lines @@
     if (entry_iter != std::end(client->known_buffer_context_ids)) {
       client->known_buffer_context_ids.erase(entry_iter);
       client->event_handler->OnBufferDestroyed(
           client->controller_id, buffer_context_iter->buffer_context_id());
     }
   }
   buffer_contexts_.erase(buffer_context_iter);
 }
 
 }  // namespace content