Reland (3rd try): Lazily initialize MessageLoop for faster thread startup

content/browser/browser_thread_impl.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/browser_thread_impl.h"
 
 #include <string>
 
 #include "base/atomicops.h"
 #include "base/bind.h"
@@ skipping 141 matching lines @@
 
 void BrowserThreadImpl::Init() {
   BrowserThreadGlobals& globals = g_globals.Get();
 
   using base::subtle::AtomicWord;
   AtomicWord* storage =
       reinterpret_cast<AtomicWord*>(&globals.thread_delegates[identifier_]);
   AtomicWord stored_pointer = base::subtle::NoBarrier_Load(storage);
   BrowserThreadDelegate* delegate =
       reinterpret_cast<BrowserThreadDelegate*>(stored_pointer);
-  if (delegate) {
+  if (delegate)
     delegate->Init();
-    message_loop()->PostTask(FROM_HERE,
-                             base::Bind(&BrowserThreadDelegate::InitAsync,
-                                        // Delegate is expected to exist for the
-                                        // duration of the thread's lifetime
-                                        base::Unretained(delegate)));
-  }
 }
 
 // We disable optimizations for this block of functions so the compiler doesn't
 // merge them all together.
 MSVC_DISABLE_OPTIMIZE()
 MSVC_PUSH_DISABLE_WARNING(4748)
 
 NOINLINE void BrowserThreadImpl::UIThreadRun(base::MessageLoop* message_loop) {
   volatile int line_number = __LINE__;
   Thread::Run(message_loop);
@@ skipping 113 matching lines @@
   globals.threads[identifier_] = NULL;
 #ifndef NDEBUG
   // Double check that the threads are ordered correctly in the enumeration.
   for (int i = identifier_ + 1; i < ID_COUNT; ++i) {
     DCHECK(!globals.threads[i]) <<
         "Threads must be listed in the reverse order that they die";
   }
 #endif
 }
 
+bool BrowserThreadImpl::StartWithOptions(const Options& options) {
+  // The global thread table needs to be locked while a new thread is
+  // starting, as the new thread can asynchronously start touching the
+  // table (and other thread's message_loop).
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
+  return Thread::StartWithOptions(options);
+}
+
 // static
 bool BrowserThreadImpl::PostTaskHelper(
     BrowserThread::ID identifier,
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     base::TimeDelta delay,
     bool nestable) {
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
   // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
   // order of lifetime.  So no need to lock if we know that the target thread
@@ skipping 227 matching lines @@
   AtomicWord* storage = reinterpret_cast<AtomicWord*>(
       &globals.thread_delegates[identifier]);
   AtomicWord old_pointer = base::subtle::NoBarrier_AtomicExchange(
       storage, reinterpret_cast<AtomicWord>(delegate));
 
   // This catches registration when previously registered.
   DCHECK(!delegate || !old_pointer);
 }
 
 }  // namespace content