Replace CHECK with CHECK_EQ in MediaStreamManager.

This CHECK should be removed since it is being hit in rare cases.
This first CL is to try to gather more information in clustefuzz
reports about the state when the CHECK is hit, since we have been
unable to reproduce it locally.
The CHECK will be removed in a follow-up CL.

Bug: 871714
Change-Id: Iefed096801002e8f4d022723c07c876ff10b0014
Reviewed-on: https://chromium-review.googlesource.com/1165542Reviewed-by: Florent Castelli <orphis@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581282}

content/browser/renderer_host/media/media_stream_manager.cc

@@ -1422,7 +1422,7 @@ void MediaStreamManager::Opened(MediaStreamType stream_type,
     for (MediaStreamDevice& device : request->devices) {
       if (device.type == stream_type &&
           device.session_id == capture_session_id) {
-        CHECK(request->state(device.type) == MEDIA_REQUEST_STATE_OPENING);
+        CHECK_EQ(request->state(device.type), MEDIA_REQUEST_STATE_OPENING);
         // We've found a matching request.
         request->SetState(device.type, MEDIA_REQUEST_STATE_DONE);