Make WeakPtr use SequenceChecker instead of ThreadChecker

base/thread_task_runner_handle.cc

Index: base/thread_task_runner_handle.cc
diff --git a/base/thread_task_runner_handle.cc b/base/thread_task_runner_handle.cc
index d1b07aaaf012f9f63a7282de5fb758b6a8503e7d..8c073880c76ea2e5b0a5f5fa37ebb183f71f4816 100644
--- a/base/thread_task_runner_handle.cc
+++ b/base/thread_task_runner_handle.cc
@@ -4,6 +4,8 @@
 
 #include "base/thread_task_runner_handle.h"
 
+#include <cstddef>
+
 #include "base/lazy_instance.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_local.h"
@@ -18,10 +20,17 @@ base::LazyInstance<base::ThreadLocalPointer<ThreadTaskRunnerHandle> >
 }  // namespace
 
 // static
-scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
+scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::GetIfExists() {
   ThreadTaskRunnerHandle* current = lazy_tls_ptr.Pointer()->Get();
-  DCHECK(current);
-  return current->task_runner_;
+  return current ? current->task_runner_ : NULL;
+}
+
+// static
+scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
+  const scoped_refptr<SingleThreadTaskRunner>& thread_task_runner =
+      GetIfExists();
+  CHECK(thread_task_runner.get());
+  return thread_task_runner;

[jar (doing other things), 2013/02/16 02:37:27]

nit: List methods after constructors and destructors.  

 }
 
 ThreadTaskRunnerHandle::ThreadTaskRunnerHandle(