Support tooltip for HoverHighlightView

BUG=

Review URL: https://codereview.chromium.org/1466393002

Cr-Commit-Position: refs/heads/master@{#361308}

ash/system/tray/hover_highlight_view.cc

@@ -50,6 +50,14 @@ HoverHighlightView::HoverHighlightView(ViewClickListener* listener)
 HoverHighlightView::~HoverHighlightView() {
 }
 
+bool HoverHighlightView::GetTooltipText(const gfx::Point& p,
+                                        base::string16* tooltip) const {
+  if (tooltip_.empty())
+    return false;
+  *tooltip = tooltip_;
+  return true;
+}
+
 void HoverHighlightView::AddIconAndLabel(const gfx::ImageSkia& image,
                                          const base::string16& text,
                                          bool highlight) {

ash/system/tray/hover_highlight_view.h

@@ -26,6 +26,10 @@ class HoverHighlightView : public ActionableView {
   explicit HoverHighlightView(ViewClickListener* listener);
   ~HoverHighlightView() override;
 
+  // views::View
+  bool GetTooltipText(const gfx::Point& p,
+                      base::string16* tooltip) const override;
+
   // Convenience function for adding an icon and a label. This also sets the
   // accessible name.
   void AddIconAndLabel(const gfx::ImageSkia& image,
@@ -66,6 +70,8 @@ class HoverHighlightView : public ActionableView {
 
   bool hover() const { return hover_; }
 
+  void set_tooltip(const base::string16& tooltip) { tooltip_ = tooltip; }
+
  protected:
   // Overridden from views::View.
   void GetAccessibleState(ui::AXViewState* state) override;
@@ -103,6 +109,7 @@ class HoverHighlightView : public ActionableView {
   bool expandable_;
   bool checkable_;
   bool checked_;
+  base::string16 tooltip_;
 
   DISALLOW_COPY_AND_ASSIGN(HoverHighlightView);
 };