Enable logging from Chromoting client plugin in PNaCl.

Now all LOG() messages are forwarded from the PNaCl plugin to the
webapp. Previously this feature was enabled only for native Debug
builds.

Review URL: https://codereview.chromium.org/553743002

Cr-Commit-Position: refs/heads/master@{#293893}

remoting/client/plugin/chromoting_instance.cc

@@ -228,6 +228,9 @@ ChromotingInstance::ChromotingInstance(PP_Instance pp_instance)
   thread_wrapper_.reset(
       new jingle_glue::JingleThreadWrapper(plugin_task_runner_));
   media::InitializeCPUSpecificYUVConversions();
+
+  // Register a global log handler.
+  ChromotingInstance::RegisterLogMessageHandler();
 #else
   jingle_glue::JingleThreadWrapper::EnsureForCurrentMessageLoop();
 #endif