Fix base::internal::WeakReference::Flag to be RefCountedThreadSafe.

This allows a base::WeakPtr to be deleted on a different thread, which will modify the refcount on Flag.

BUG=none
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=81142

Review URL: http://codereview.chromium.org/6826034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@81148 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 23 insertions, 24 deletions

diff --git a/base/memory/weak_ptr.cc b/base/memory/weak_ptr.cc
index fb09219..30c777c 100644
--- a/base/memory/weak_ptr.cc
+++ b/base/memory/weak_ptr.cc
@@ -10,31 +10,21 @@ namespace internal {
 WeakReference::Flag::Flag(Flag** handle) : handle_(handle) {
 }
 
-WeakReference::Flag::~Flag() {
-  if (handle_)
-    *handle_ = NULL;
-}
-
-void WeakReference::Flag::AddRef() const {
-  DCHECK(CalledOnValidThread());
-  RefCounted<Flag>::AddRef();
-}
-
-void WeakReference::Flag::Release() const {
-  DCHECK(CalledOnValidThread());
-  RefCounted<Flag>::Release();
-}
-
 void WeakReference::Flag::Invalidate() {
-  DCHECK(CalledOnValidThread());
+  DCHECK(thread_checker_.CalledOnValidThread());
   handle_ = NULL;
 }
 
 bool WeakReference::Flag::IsValid() const {
-  DCHECK(CalledOnValidThread());
+  DCHECK(thread_checker_.CalledOnValidThread());
   return handle_ != NULL;
 }
 
+WeakReference::Flag::~Flag() {
+  if (handle_)
+    *handle_ = NULL;
+}
+
 WeakReference::WeakReference() {
 }
 
diff --git a/base/memory/weak_ptr.h b/base/memory/weak_ptr.h
index edb9d93..0c6b4a7 100644
--- a/base/memory/weak_ptr.h
+++ b/base/memory/weak_ptr.h
@@ -55,7 +55,7 @@
 #include "base/base_api.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/threading/thread_checker.h"
 
 namespace base {
 
@@ -65,19 +65,23 @@ namespace internal {
 
 class BASE_API WeakReference {
  public:
-  class Flag : public RefCounted<Flag>, public base::NonThreadSafe {
+  // While Flag is bound to a specific thread, it may be deleted from another
+  // via base::WeakPtr::~WeakPtr().
+  class Flag : public RefCountedThreadSafe<Flag> {
    public:
-    Flag(Flag** handle);
-    ~Flag();
+    explicit Flag(Flag** handle);
 
-    void AddRef() const;
-    void Release() const;
     void Invalidate();
     bool IsValid() const;
 
-    void DetachFromThread() { base::NonThreadSafe::DetachFromThread(); }
+    void DetachFromThread() { thread_checker_.DetachFromThread(); }
 
    private:
+    friend class base::RefCountedThreadSafe<Flag>;
+
+    ~Flag();
+
+    ThreadChecker thread_checker_;
     Flag** handle_;
   };
 
@@ -235,6 +239,11 @@ class WeakPtrFactory {
     return weak_reference_owner_.HasRefs();
   }
 
+  // Indicates that this object will be used on another thread from now on.
+  void DetachFromThread() {
+    weak_reference_owner_.DetachFromThread();
+  }
+
  private:
   internal::WeakReferenceOwner weak_reference_owner_;
   T* ptr_;