[cc] Make LayerImpls point at LayerTreeImpl instead of LTHI

cc/scrollbar_animation_controller_linear_fade_unittest.cc

Index: cc/scrollbar_animation_controller_linear_fade_unittest.cc
diff --git a/cc/scrollbar_animation_controller_linear_fade_unittest.cc b/cc/scrollbar_animation_controller_linear_fade_unittest.cc
index dd941c1891a663b1792a6d42d871feed0cb1b19b..0312bc95dd4a012ffd67b955690a1d777660f322 100644
--- a/cc/scrollbar_animation_controller_linear_fade_unittest.cc
+++ b/cc/scrollbar_animation_controller_linear_fade_unittest.cc
@@ -23,10 +23,10 @@ public:
 protected:
     virtual void SetUp()
     {
-        m_scrollLayer = LayerImpl::create(&m_hostImpl, 1);
-        m_scrollLayer->addChild(LayerImpl::create(&m_hostImpl, 2));
+        m_scrollLayer = LayerImpl::create(m_hostImpl.activeTree(), 1);
+        m_scrollLayer->addChild(LayerImpl::create(m_hostImpl.activeTree(), 2));
         m_contentLayer = m_scrollLayer->children()[0];
-        m_scrollbarLayer = ScrollbarLayerImpl::create(&m_hostImpl, 3);
+        m_scrollbarLayer = ScrollbarLayerImpl::create(m_hostImpl.activeTree(), 3);
 
         m_scrollLayer->setMaxScrollOffset(gfx::Vector2d(50, 50));
         m_contentLayer->setBounds(gfx::Size(50, 50));