Rewrite scoped_ptr<T>(NULL) to use the default ctor in ash/.

ash/wm/workspace/workspace_window_resizer_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 "ash/wm/workspace/workspace_window_resizer.h"
 
 #include "ash/ash_switches.h"
 #include "ash/display/display_controller.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
@@ skipping 49 matching lines @@
   }
 
   gfx::Size min_size_;
   gfx::Size max_size_;
 
   DISALLOW_COPY_AND_ASSIGN(TestWindowDelegate);
 };
 
 class WorkspaceWindowResizerTest : public test::AshTestBase {
  public:
-  WorkspaceWindowResizerTest() : window_(NULL) {}
+  WorkspaceWindowResizerTest() {}
   virtual ~WorkspaceWindowResizerTest() {}
 
   virtual void SetUp() OVERRIDE {
     AshTestBase::SetUp();
     UpdateDisplay(base::StringPrintf("800x%d", kRootHeight));
 
     aura::RootWindow* root = Shell::GetPrimaryRootWindow();
     gfx::Rect root_bounds(root->bounds());
 #if defined(OS_WIN)
     // RootWindow and Display can't resize on Windows Ash.
@@ skipping 1499 matching lines @@
   ASSERT_TRUE(resizer.get());
   // Move it 50 to the left, which should contract w1 and expand w2-3.
   resizer->Drag(CalculateDragPoint(*resizer, -50, 0), 0);
   EXPECT_EQ("100,100 98x100", window_->bounds().ToString());
   EXPECT_EQ("198,100 101x100", window2_->bounds().ToString());
   EXPECT_EQ("299,100 101x100", window3_->bounds().ToString());
 }
 
 }  // namespace internal
 }  // namespace ash