Do not set low priority on background tabs.

content/browser/child_process_launcher.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/child_process_launcher.h"
 
 #include <utility>  // For std::pair.
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 492 matching lines @@
   // it'll reap the process.  However, if GetTerminationStatus didn't
   // reap the child (because it was still running), we'll need to
   // Terminate via ProcessWatcher. So we can't close the handle here.
   if (context_->termination_status_ != base::TERMINATION_STATUS_STILL_RUNNING)
     context_->process_.Close();
 
   return context_->termination_status_;
 }
 
 void ChildProcessLauncher::SetProcessBackgrounded(bool background) {
-  BrowserThread::PostTask(
-      BrowserThread::PROCESS_LAUNCHER, FROM_HERE,
-      base::Bind(
-          &ChildProcessLauncher::Context::SetProcessBackgrounded,
-          GetHandle(), background));
+  // TODO(wfh): re-enable this after testing if dropping the priority of
+  // backgrounded tabs is the root cause of http://crbug.com/381820.
+  // BrowserThread::PostTask(
+  //     BrowserThread::PROCESS_LAUNCHER, FROM_HERE,
+  //     base::Bind(
+  //         &ChildProcessLauncher::Context::SetProcessBackgrounded,
+  //         GetHandle(), background));
 }
 
 void ChildProcessLauncher::SetTerminateChildOnShutdown(
     bool terminate_on_shutdown) {
   if (context_.get())
     context_->set_terminate_child_on_shutdown(terminate_on_shutdown);
 }
 
 }  // namespace content