Add MD Ink Drop Layers to InkDropHost only when a ripple/hover is active.

ui/views/views.gyp

Index: ui/views/views.gyp
diff --git a/ui/views/views.gyp b/ui/views/views.gyp
index b43355fd5190ab00aafd8d25fe38dc7a0ea66399..47c858ad5e4df2f2522720ed112d28122bbb5632 100644
--- a/ui/views/views.gyp
+++ b/ui/views/views.gyp
@@ -32,6 +32,7 @@
       'animation/ink_drop_host_view.h',
       'animation/ink_drop_hover.cc',
       'animation/ink_drop_hover.h',
+      'animation/ink_drop_hover_observer.h',
       'animation/ink_drop_painted_layer_delegates.cc',
       'animation/ink_drop_painted_layer_delegates.h',
       'animation/ink_drop_state.cc',
@@ -504,6 +505,8 @@
       'animation/test/test_ink_drop_animation_observer_helper.h',
       'animation/test/test_ink_drop_host.cc',
       'animation/test/test_ink_drop_host.h',
+      'animation/test/test_ink_drop_hover_observer.cc',
+      'animation/test/test_ink_drop_hover_observer.h',
       'animation/test/test_ink_drop_delegate.cc',
       'animation/test/test_ink_drop_delegate.h',
       'controls/textfield/textfield_test_api.cc',