Make WeakPtr use SequenceChecker instead of ThreadChecker

base/memory/weak_ptr.cc

Index: base/memory/weak_ptr.cc
diff --git a/base/memory/weak_ptr.cc b/base/memory/weak_ptr.cc
index 9dec8fd6db9c29956673a79326efa4b22af2f3ad..e4e43b1d1b21e7ae5f6a0484d0835eae26d88c12 100644
--- a/base/memory/weak_ptr.cc
+++ b/base/memory/weak_ptr.cc
@@ -3,25 +3,33 @@
 // found in the LICENSE file.
 
 #include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
 
 namespace base {
 namespace internal {
 
-WeakReference::Flag::Flag() : is_valid_(true) {
+WeakReference::Flag::Flag()
+    : sequence_checker_(ThreadTaskRunnerHandle::GetIfExists()),
+      is_valid_(true) {
 }
 
 void WeakReference::Flag::Invalidate() {
   // The flag being invalidated with a single ref implies that there are no
   // weak pointers in existence. Allow deletion on other thread in this case.
-  DCHECK(thread_checker_.CalledOnValidThread() || HasOneRef());
+  DCHECK(sequence_checker_.CalledInSequence() || HasOneRef());

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

nit: Although the semantics may be as intended (to replace CalledOnValidThread),
this method name is very confusing.

Can you suggest a better name, or perhaps even (worst case) have another method
that CalledOnValidThread() or maybe CalledOnConsistentThread()?

   is_valid_ = false;
 }
 
 bool WeakReference::Flag::IsValid() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(sequence_checker_.CalledInSequence());
   return is_valid_;
 }
 
+void WeakReference::Flag::DetachFromThread() {
+  sequence_checker_.ChangeSequence(ThreadTaskRunnerHandle::GetIfExists());

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

nit: This "ChangeSequence" also seems confusing :-(.

Maybe it would help if at least the slot was called something like:
consistent_thread_checker_ 
or (though even this bothers me):
valide_thread_checker_

In truth, I  again feel like the method name does not help the reader understand
what this is doing, or why we're calling it :-(.

Suggestions?

+}
+
 WeakReference::Flag::~Flag() {
 }