Remove CHECK(!g_webrtc_logging_delegate) for --single-process model

content/renderer/media/webrtc_logging.cc

 // Copyright 2013 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/renderer/media/webrtc_logging.h"
 
+#include "base/command_line.h"
 #include "base/time/time.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/renderer/webrtc_log_message_delegate.h"
 #include "third_party/webrtc/overrides/webrtc/base/logging.h"
 
 namespace content {
 
-// Shall only be set once and never go back to NULL.
+// Shall only be set once and never go back to NULL
+// except for single process model.
 WebRtcLogMessageDelegate* g_webrtc_logging_delegate = NULL;
 
 void InitWebRtcLoggingDelegate(WebRtcLogMessageDelegate* delegate) {
-  CHECK(!g_webrtc_logging_delegate);
+  // We will not check g_webrtc_logging_delegate in single process mode,
+  // since g_webrtc_logging_delegate may shared by two RenderThreads in
+  // the same browser process.
+  CHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
+             switches::kSingleProcess) ||
+        !g_webrtc_logging_delegate);

[tommi (sloooow) - chröme, 2015/03/04 13:23:20]

In the case where g_webrtc_logging_delegate is not null, what value will this be
set to?  Will it overwrite the previous value or will it be assigned the same
value it is already set to?

[jinlong.zhai, 2015/03/05 01:50:17]

In this case, it will overwrite the provious value. And I think this feature is
just to notify logging message, it is OK to do this no matter by new value or
previous value in single process.

I also consider another way to re-landing this: create g_webrtc_logging_delegate
as a tls on IO thread, and also we must make sure every place where
WebRtcLogMessage be called should do on IO thread or it will not work by add
CHECK(g_webrtc_logging_delegate_tls->poniter()->Get()) << "WebRtcLogMessage
should be called on IO thread".

WDYT?

   CHECK(delegate);
 
   g_webrtc_logging_delegate = delegate;
 }
 
 void InitWebRtcLogging() {
   // Log messages from Libjingle should not have timestamps.
   rtc::InitDiagnosticLoggingDelegateFunction(&WebRtcLogMessage);
 }
 
 void WebRtcLogMessage(const std::string& message) {
   if (g_webrtc_logging_delegate)
     g_webrtc_logging_delegate->LogMessage(message);
 }
 
 }  // namespace content