Adding ripple effect for clicks on MD slider

ui/views/controls/md_slider.h

Index: ui/views/controls/md_slider.h
diff --git a/ui/views/controls/md_slider.h b/ui/views/controls/md_slider.h
index d9ceeecf0ca3785f5792e88e933e70acd777d052..e4d1c92dfcefb003c8fe1dbaca44546e8b4924dd 100644
--- a/ui/views/controls/md_slider.h
+++ b/ui/views/controls/md_slider.h
@@ -31,8 +31,16 @@ class VIEWS_EXPORT MdSlider : public Slider {
   int GetThumbWidth() override;
 
  private:
+  // views::View:
+  bool OnMousePressed(const ui::MouseEvent& event) override;

[bruthig, 2016/09/12 17:16:48]

What about touch and keyboard interactions?  I assume we would want the
highlight for touch for sure but don't know about keyboard.

It might make sense to re-use the Slider::PrepareForMove() method as
MousePressed() and OnGestureEvent() already call this.

[yiyix, 2016/09/20 20:25:46]

Instead of override functions, I created a new function called SetFocus, which
will be set when the slider is selected. Please take a look at this new
approach.

+  void OnMouseReleased(const ui::MouseEvent& event) override;
+
   // Record whether the slider is in the active state or the disabled state.
   bool is_active_;
+
+  // It is true if there is a press event or a touch event in this view
+  // currently; otherwise, it is false.
+  bool is_pressed_;
 };
 
 }  // namespace views