Hook up the SequencedWorkerPool to the browser thread.

content/browser/browser_thread_impl.cc

Index: content/browser/browser_thread_impl.cc
===================================================================
--- content/browser/browser_thread_impl.cc	(revision 117955)
+++ content/browser/browser_thread_impl.cc	(working copy)
@@ -9,6 +9,7 @@
 #include "base/lazy_instance.h"
 #include "base/message_loop.h"
 #include "base/message_loop_proxy.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace content {
@@ -27,25 +28,38 @@
   "Chrome_IOThread",  // IO
 };
 
-// This lock protects |g_browser_threads|.  Do not read or modify that
-// array without holding this lock.  Do not block while holding this
-// lock.
-base::LazyInstance<base::Lock,
-                   base::LeakyLazyInstanceTraits<base::Lock> >
-    g_lock = LAZY_INSTANCE_INITIALIZER;
+struct BrowserThreadGlobals {
+  BrowserThreadGlobals()
+      : blocking_pool(new base::SequencedWorkerPool(3, "BrowserBlocking")) {
+    memset(threads, 0,
+           BrowserThread::ID_COUNT * sizeof(BrowserThreadImpl*));
+    memset(thread_delegates, 0,
+           BrowserThread::ID_COUNT * sizeof(BrowserThreadDelegate*));
+  }
 
-// This array is protected by |g_lock|.  The threads are not owned by this
-// array. Typically, the threads are owned on the UI thread by
-// content::BrowserMainLoop.  BrowserThreadImpl objects remove
-// themselves from this array upon destruction.
-static BrowserThreadImpl* g_browser_threads[BrowserThread::ID_COUNT];
+  // This lock protects |threads|. Do not read or modify that array
+  // without holding this lock. Do not block while holding this lock.
+  base::Lock lock;
 
-// Only atomic operations are used on this array.  The delegates are
-// not owned by this array, rather by whoever calls
-// BrowserThread::SetDelegate.
-static BrowserThreadDelegate* g_browser_thread_delegates[
-    BrowserThread::ID_COUNT];
+  // This array is protected by |lock|. The threads are not owned by this
+  // array. Typically, the threads are owned on the UI thread by
+  // content::BrowserMainLoop. BrowserThreadImpl objects remove themselves from
+  // this array upon destruction.
+  BrowserThreadImpl* threads[BrowserThread::ID_COUNT];
 
+  // Only atomic operations are used on this array. The delegates are not owned
+  // by this array, rather by whoever calls BrowserThread::SetDelegate.
+  BrowserThreadDelegate* thread_delegates[BrowserThread::ID_COUNT];
+
+  // This pointer is deliberately leaked on shutdown. This allows the pool to
+  // implement "continue on shutdown" semantics.
+  base::SequencedWorkerPool* blocking_pool;
+};
+
+base::LazyInstance<BrowserThreadGlobals,
+                   base::LeakyLazyInstanceTraits<BrowserThreadGlobals> >
+    g_globals = LAZY_INSTANCE_INITIALIZER;
+
 }  // namespace
 
 BrowserThreadImpl::BrowserThreadImpl(ID identifier)
@@ -62,10 +76,18 @@
   Initialize();
 }
 
+// static
+void BrowserThreadImpl::ShutdownThreadPool() {
+  BrowserThreadGlobals& globals = g_globals.Get();
+  globals.blocking_pool->Shutdown();
+}
+
 void BrowserThreadImpl::Init() {
+  BrowserThreadGlobals& globals = g_globals.Get();
+
   using base::subtle::AtomicWord;
   AtomicWord* storage =
-      reinterpret_cast<AtomicWord*>(&g_browser_thread_delegates[identifier_]);
+      reinterpret_cast<AtomicWord*>(&globals.thread_delegates[identifier_]);
   AtomicWord stored_pointer = base::subtle::NoBarrier_Load(storage);
   BrowserThreadDelegate* delegate =
       reinterpret_cast<BrowserThreadDelegate*>(stored_pointer);
@@ -74,9 +96,11 @@
 }
 
 void BrowserThreadImpl::CleanUp() {
+  BrowserThreadGlobals& globals = g_globals.Get();
+
   using base::subtle::AtomicWord;
   AtomicWord* storage =
-      reinterpret_cast<AtomicWord*>(&g_browser_thread_delegates[identifier_]);
+      reinterpret_cast<AtomicWord*>(&globals.thread_delegates[identifier_]);
   AtomicWord stored_pointer = base::subtle::NoBarrier_Load(storage);
   BrowserThreadDelegate* delegate =
       reinterpret_cast<BrowserThreadDelegate*>(stored_pointer);
@@ -86,10 +110,12 @@
 }
 
 void BrowserThreadImpl::Initialize() {
-  base::AutoLock lock(g_lock.Get());
+  BrowserThreadGlobals& globals = g_globals.Get();
+
+  base::AutoLock lock(globals.lock);
   DCHECK(identifier_ >= 0 && identifier_ < ID_COUNT);
-  DCHECK(g_browser_threads[identifier_] == NULL);
-  g_browser_threads[identifier_] = this;
+  DCHECK(globals.threads[identifier_] == NULL);
+  globals.threads[identifier_] = this;
 }
 
 BrowserThreadImpl::~BrowserThreadImpl() {
@@ -98,12 +124,13 @@
   // the right BrowserThread.
   Stop();
 
-  base::AutoLock lock(g_lock.Get());
-  g_browser_threads[identifier_] = NULL;
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
+  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(!g_browser_threads[i]) <<
+    DCHECK(!globals.threads[i]) <<
         "Threads must be listed in the reverse order that they die";
   }
 #endif
@@ -128,11 +155,12 @@
       GetCurrentThreadIdentifier(&current_thread) &&
       current_thread <= identifier;
 
+  BrowserThreadGlobals& globals = g_globals.Get();
   if (!guaranteed_to_outlive_target_thread)
-    g_lock.Get().Acquire();
+    globals.lock.Acquire();
 
-  MessageLoop* message_loop = g_browser_threads[identifier] ?
-      g_browser_threads[identifier]->message_loop() : NULL;
+  MessageLoop* message_loop = globals.threads[identifier] ?
+      globals.threads[identifier]->message_loop() : NULL;
   if (message_loop) {
     if (nestable) {
       message_loop->PostDelayedTask(from_here, task, delay_ms);
@@ -142,7 +170,7 @@
   }
 
   if (!guaranteed_to_outlive_target_thread)
-    g_lock.Get().Release();
+    globals.lock.Release();
 
   return !!message_loop;
 }
@@ -189,10 +217,32 @@
 };
 
 // static
+bool BrowserThread::PostBlockingPoolTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task) {
+  return g_globals.Get().blocking_pool->PostWorkerTask(from_here, task);
+}
+
+// static
+bool BrowserThread::PostBlockingPoolSequencedTask(
+    const std::string& sequence_token_name,
+    const tracked_objects::Location& from_here,
+    const base::Closure& task) {
+  return g_globals.Get().blocking_pool->PostNamedSequencedWorkerTask(
+      sequence_token_name, from_here, task);
+}
+
+// static
+base::SequencedWorkerPool* BrowserThread::GetBlockingPool() {
+  return g_globals.Get().blocking_pool;
+}
+
+// static
 bool BrowserThread::IsWellKnownThread(ID identifier) {
-  base::AutoLock lock(g_lock.Get());
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
   return (identifier >= 0 && identifier < ID_COUNT &&
-          g_browser_threads[identifier]);
+          globals.threads[identifier]);
 }
 
 // static
@@ -202,19 +252,21 @@
   // function.
   // http://crbug.com/63678
   base::ThreadRestrictions::ScopedAllowSingleton allow_singleton;
-  base::AutoLock lock(g_lock.Get());
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  return g_browser_threads[identifier] &&
-         g_browser_threads[identifier]->message_loop() ==
+  return globals.threads[identifier] &&
+         globals.threads[identifier]->message_loop() ==
              MessageLoop::current();
 }
 
 // static
 bool BrowserThread::IsMessageLoopValid(ID identifier) {
-  base::AutoLock lock(g_lock.Get());
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
-  return g_browser_threads[identifier] &&
-         g_browser_threads[identifier]->message_loop();
+  return globals.threads[identifier] &&
+         globals.threads[identifier]->message_loop();
 }
 
 // static
@@ -272,10 +324,11 @@
   // http://crbug.com/63678
   base::ThreadRestrictions::ScopedAllowSingleton allow_singleton;
   MessageLoop* cur_message_loop = MessageLoop::current();
+  BrowserThreadGlobals& globals = g_globals.Get();
   for (int i = 0; i < ID_COUNT; ++i) {
-    if (g_browser_threads[i] &&
-        g_browser_threads[i]->message_loop() == cur_message_loop) {
-      *identifier = g_browser_threads[i]->identifier_;
+    if (globals.threads[i] &&
+        globals.threads[i]->message_loop() == cur_message_loop) {
+      *identifier = globals.threads[i]->identifier_;
       return true;
     }
   }
@@ -285,8 +338,7 @@
 
 // static
 scoped_refptr<base::MessageLoopProxy>
-BrowserThread::GetMessageLoopProxyForThread(
-    ID identifier) {
+BrowserThread::GetMessageLoopProxyForThread(ID identifier) {
   scoped_refptr<base::MessageLoopProxy> proxy(
       new BrowserThreadMessageLoopProxy(identifier));
   return proxy;
@@ -294,8 +346,9 @@
 
 // static
 MessageLoop* BrowserThread::UnsafeGetMessageLoopForThread(ID identifier) {
-  base::AutoLock lock(g_lock.Get());
-  base::Thread* thread = g_browser_threads[identifier];
+  BrowserThreadGlobals& globals = g_globals.Get();
+  base::AutoLock lock(globals.lock);
+  base::Thread* thread = globals.threads[identifier];
   DCHECK(thread);
   MessageLoop* loop = thread->message_loop();
   return loop;
@@ -305,8 +358,9 @@
 void BrowserThread::SetDelegate(ID identifier,
                                 BrowserThreadDelegate* delegate) {
   using base::subtle::AtomicWord;
+  BrowserThreadGlobals& globals = g_globals.Get();
   AtomicWord* storage = reinterpret_cast<AtomicWord*>(
-      &g_browser_thread_delegates[identifier]);
+      &globals.thread_delegates[identifier]);
   AtomicWord old_pointer = base::subtle::NoBarrier_AtomicExchange(
       storage, reinterpret_cast<AtomicWord>(delegate));