Make WeakPtr harder to misuse.

Well, I managed to misuse it (issue caught in review), and these DCHECKS
will catch it.

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/207005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@26422 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 20 insertions, 2 deletions

diff --git a/base/weak_ptr.h b/base/weak_ptr.h
index 720beb5..2fd670b 100644
--- a/base/weak_ptr.h
+++ b/base/weak_ptr.h
@@ -72,16 +72,34 @@ class WeakReference {
   }
 
   void Invalidate() {
-    if (flag_)
+    if (flag_) {
+      DCHECK(flag_->CalledOnValidThread());
       flag_->data = false;
+    }
   }
 
-  bool is_valid() const { return flag_ && flag_->data; }
+  bool is_valid() const {
+    if (flag_) {
+      DCHECK(flag_->CalledOnValidThread());
+      return flag_->data;
+    }
+    return false;
+  }
 
  private:
   // A reference counted boolean that is true when the weak reference is valid
   // and false otherwise.
   class Flag : public RefCountedData<bool>, public NonThreadSafe {
+   public:
+    void AddRef() {
+      DCHECK(CalledOnValidThread());
+      RefCountedData<bool>::AddRef();
+    }
+
+    void Release() {
+      DCHECK(CalledOnValidThread());
+      RefCountedData<bool>::Release();
+    }
   };
 
   scoped_refptr<Flag> flag_;