Improve GetWeakPtr() to better protect against unsafe usage patterns.

base/memory/weak_ptr_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/weak_ptr.h"
 
 #include <memory>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 398 matching lines @@
 
     // The new WeakPtr is owned by background thread.
     EXPECT_EQ(target, background.DeRef(&arrow));
   }
 
   // Target can only be deleted on background thread.
   background.DeleteTarget(target);
   background.DeleteArrow(arrow);
 }
 
-TEST(WeakPtrTest, MoveOwnershipOfUnreferencedObject) {
-  BackgroundThread background;
-  background.Start();
-
-  Arrow* arrow;
-  {
-    Target target;
-    // Background thread creates WeakPtr.
-    background.CreateArrowFromTarget(&arrow, &target);
-
-    // Bind to background thread.
-    EXPECT_EQ(&target, background.DeRef(arrow));
-
-    // Release the only WeakPtr.
-    arrow->target.reset();
-
-    // Now we should be able to create a new reference from this thread.
-    arrow->target = target.AsWeakPtr();
-
-    // Re-bind to main thread.
-    EXPECT_EQ(&target, arrow->target.get());
-
-    // And the main thread can now delete the target.
-  }
-
-  delete arrow;
-}
-
 TEST(WeakPtrTest, MoveOwnershipAfterInvalidate) {
   BackgroundThread background;
   background.Start();
 
   Arrow arrow;
   std::unique_ptr<TargetWithFactory> target(new TargetWithFactory);
 
   // Bind to main thread.
   arrow.target = target->factory.GetWeakPtr();
   EXPECT_EQ(target.get(), arrow.target.get());
@@ skipping 212 matching lines @@
   // Background thread tries to delete target, binding the object to the thread.
   BackgroundThread background;
   background.Start();
   background.DeleteTarget(target.release());
 
   // Main thread attempts to dereference the target, violating thread binding.
   ASSERT_DCHECK_DEATH(arrow.target.get());
 }
 
 }  // namespace base