DevTools: Parallelize trace messages serialization.

content/browser/media/webrtc_getusermedia_browsertest.cc

Index: content/browser/media/webrtc_getusermedia_browsertest.cc
diff --git a/content/browser/media/webrtc_getusermedia_browsertest.cc b/content/browser/media/webrtc_getusermedia_browsertest.cc
index d2e69eed076d5ef66b78a3d502423a6607a72459..8cd00dce04703f741a8ec88dd476d55e6cae2e8d 100644
--- a/content/browser/media/webrtc_getusermedia_browsertest.cc
+++ b/content/browser/media/webrtc_getusermedia_browsertest.cc
@@ -96,6 +96,7 @@ class WebRtcGetUserMediaBrowserTest: public WebRtcContentBrowserTest {
     CHECK(message_loop_runner_.get() == NULL)
         << "Calling StopTracing more than once";
     trace_log_->SetDisabled();
+    message_loop_proxy_ = base::MessageLoopProxy::current();
     message_loop_runner_ = new MessageLoopRunner;
     trace_log_->Flush(base::Bind(
         &WebRtcGetUserMediaBrowserTest::OnTraceDataCollected,
@@ -107,6 +108,13 @@ class WebRtcGetUserMediaBrowserTest: public WebRtcContentBrowserTest {
       const scoped_refptr<base::RefCountedString>& events_str_ptr,
       bool has_more_events) {
     CHECK(!has_more_events);
+    if (!message_loop_proxy_->BelongsToCurrentThread()) {
+      message_loop_proxy_->PostTask(
+          FROM_HERE,
+          Bind(&WebRtcGetUserMediaBrowserTest::OnTraceDataCollected,
+               base::Unretained(this), events_str_ptr, has_more_events));
+      return;
+    }
     recorded_trace_data_ = events_str_ptr;
     message_loop_runner_->Quit();
   }
@@ -234,6 +242,7 @@ class WebRtcGetUserMediaBrowserTest: public WebRtcContentBrowserTest {
   base::debug::TraceLog* trace_log_;
   scoped_refptr<base::RefCountedString> recorded_trace_data_;
   scoped_refptr<MessageLoopRunner> message_loop_runner_;
+  scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
 };
 
 // These tests will all make a getUserMedia call with different constraints and