Add ink drop masking to TrayBackgroundView

ash/common/system/tray/tray_background_view.cc

Index: ash/common/system/tray/tray_background_view.cc
diff --git a/ash/common/system/tray/tray_background_view.cc b/ash/common/system/tray/tray_background_view.cc
index 8884948369ebfe1982dc0f33ddc6589f92eee130..e35b85cc2ac164cf111df2f3406b1f4e44f1e5eb 100644
--- a/ash/common/system/tray/tray_background_view.cc
+++ b/ash/common/system/tray/tray_background_view.cc
@@ -35,6 +35,7 @@
 #include "ui/gfx/transform.h"
 #include "ui/views/animation/flood_fill_ink_drop_ripple.h"
 #include "ui/views/animation/ink_drop_highlight.h"
+#include "ui/views/animation/ink_drop_mask.h"
 #include "ui/views/background.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/wm/core/window_animations.h"
@@ -376,6 +377,22 @@ void TrayBackgroundView::AboutToRequestFocusFromTabTraversal(bool reverse) {
     v->AboutToRequestFocusFromTabTraversal(reverse);
 }
 
+void TrayBackgroundView::AddInkDropLayer(ui::Layer* ink_drop_layer) {
+  gfx::Rect local_bounds = GetLocalBounds();
+  ink_drop_layer->SetBounds(local_bounds);

[bruthig, 2016/11/11 20:16:43]

Capturing offline discussion:
Let's move the ownership of setting the bounds on the ink drop root layer into
the InkDropImpl. This will reduce the burden on AddInkDropLayer() overrides to
do the right thing.

We will have to add an InkDrop::BoundsUpdated() method so the host view can
notify the ink drop instance of the new bounds/size.

[mohsen, 2016/11/13 23:31:28]

Done.

+  ink_drop_mask_.reset(new views::RoundRectInkDropMask(
+      local_bounds, GetBackgroundBounds(GetContentsBounds(), shelf_alignment_),
+      kTrayRoundedBorderRadius));
+  ink_drop_layer->SetMaskLayer(ink_drop_mask_->layer());
+  ActionableView::AddInkDropLayer(ink_drop_layer);
+}
+
+void TrayBackgroundView::RemoveInkDropLayer(ui::Layer* ink_drop_layer) {
+  ActionableView::RemoveInkDropLayer(ink_drop_layer);
+  ink_drop_layer->SetMaskLayer(nullptr);
+  ink_drop_mask_.reset();
+}
+
 std::unique_ptr<views::InkDropRipple> TrayBackgroundView::CreateInkDropRipple()
     const {
   return base::MakeUnique<views::FloodFillInkDropRipple>(