Move scroll event handlers from layer to layer tree view.

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index 9313c4d1fa3c0d63e915eb093351808189ebf8b9..560df10a90961065e4cdb7e918e0332a2b8cb9a4 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -1334,6 +1334,7 @@ class LayerTreeHostTestCommit : public LayerTreeHostTest {
     layer_tree_host()->SetViewportSize(gfx::Size(20, 20));
     layer_tree_host()->set_background_color(SK_ColorGRAY);
     layer_tree_host()->SetHaveWheelEventHandlers(true);
+    layer_tree_host()->SetHaveScrollEventHandlers(true);
 
     PostSetNeedsCommitToMainThread();
   }
@@ -1342,6 +1343,7 @@ class LayerTreeHostTestCommit : public LayerTreeHostTest {
     EXPECT_EQ(gfx::Size(20, 20), impl->DrawViewportSize());
     EXPECT_EQ(SK_ColorGRAY, impl->active_tree()->background_color());
     EXPECT_TRUE(impl->active_tree()->have_wheel_event_handlers());
+    EXPECT_TRUE(impl->active_tree()->have_scroll_event_handlers());
 
     EndTest();
   }