cc: Remove use of PassAs() and constructor-casting with scoped_ptr.

cc/trees/layer_tree_host_unittest_scroll.cc

 // Copyright 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 "cc/trees/layer_tree_host.h"
 
 #include "base/memory/weak_ptr.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/picture_layer.h"
@@ skipping 1103 matching lines @@
                                     base::MessageLoopProxy::current(),
                                     impl_thread.message_loop_proxy());
 
   impl_thread.message_loop_proxy()
       ->PostTask(FROM_HERE,
                  base::Bind(&BindInputHandlerOnCompositorThread,
                             layer_tree_host->GetInputHandler(),
                             base::Unretained(&input_handler_client)));
 
   layer_tree_host->DidStopFlinging();
-  layer_tree_host.reset();
+  layer_tree_host = nullptr;
   impl_thread.Stop();
   EXPECT_TRUE(received_stop_flinging);
 }
 
 class LayerTreeHostScrollTestLayerStructureChange
     : public LayerTreeHostScrollTest {
  public:
   LayerTreeHostScrollTestLayerStructureChange()
       : scroll_destroy_whole_tree_(false) {}
 
@@ skipping 80 matching lines @@
   RunTest(true, false, true);
 }
 
 TEST_F(LayerTreeHostScrollTestLayerStructureChange, ScrollDestroyWholeTree) {
   scroll_destroy_whole_tree_ = true;
   RunTest(true, false, true);
 }
 
 }  // namespace
 }  // namespace cc