Clean LayerImpl's scroll offset callers in unit tests.

cc/trees/layer_tree_host_unittest.cc

 // Copyright 2011 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 <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 52 matching lines @@
 #include "ui/gfx/geometry/vector2d_conversions.h"
 
 using testing::_;
 using testing::AnyNumber;
 using testing::AtLeast;
 using testing::Mock;
 
 namespace cc {
 namespace {
 
-class LayerTreeHostTest : public LayerTreeTest {};
+class LayerTreeHostTest : public LayerTreeTest {
+ public:
+  ScrollTree* scroll_tree(LayerImpl* layer_impl) {

[ajuma, 2016/03/07 19:10:19]

Is this called anywhere?

[sunxd, 2016/03/09 01:51:20]

Done.

+    return &layer_impl->layer_tree_impl()->property_trees()->scroll_tree;
+  }
+};
 
 class LayerTreeHostTestHasImplThreadTest : public LayerTreeHostTest {
  public:
   LayerTreeHostTestHasImplThreadTest() : threaded_(false) {}
 
   void RunTest(CompositorMode mode, bool delegating_renderer) override {
     threaded_ = mode == CompositorMode::THREADED;
     LayerTreeHostTest::RunTest(mode, delegating_renderer);
   }
 
@@ skipping 6586 matching lines @@
     EndTest();
   }
 
   void AfterTest() override {}
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestPaintedDeviceScaleFactor);
 
 }  // namespace
 }  // namespace cc