Tab, TabStrip: Added GetClassName override.

This helps with debugging a TabbedPane views hierarchy as you can print
the proper class names of Tabs and TabStrips inside.

Review URL: https://codereview.chromium.org/889453004

Cr-Commit-Position: refs/heads/master@{#313672}

ui/views/controls/tabbed_pane/tabbed_pane.cc

@@ -34,6 +34,9 @@ const char TabbedPane::kViewClassName[] = "TabbedPane";
 // The tab view shown in the tab strip.
 class Tab : public View {
  public:
+  // Internal class name.
+  static const char kViewClassName[];
+
   Tab(TabbedPane* tabbed_pane, const base::string16& title, View* contents);
   ~Tab() override;
 
@@ -49,6 +52,7 @@ class Tab : public View {
   void OnGestureEvent(ui::GestureEvent* event) override;
   gfx::Size GetPreferredSize() const override;
   void Layout() override;
+  const char* GetClassName() const override;
 
  private:
   enum TabState {
@@ -72,12 +76,16 @@ class Tab : public View {
 // The tab strip shown above the tab contents.
 class TabStrip : public View {
  public:
+  // Internal class name.
+  static const char kViewClassName[];
+
   explicit TabStrip(TabbedPane* tabbed_pane);
   ~TabStrip() override;
 
   // Overridden from View:
   gfx::Size GetPreferredSize() const override;
   void Layout() override;
+  const char* GetClassName() const override;
   void OnPaint(gfx::Canvas* canvas) override;
 
  private:
@@ -86,6 +94,9 @@ class TabStrip : public View {
   DISALLOW_COPY_AND_ASSIGN(TabStrip);
 };
 
+// static
+const char Tab::kViewClassName[] = "Tab";
+
 Tab::Tab(TabbedPane* tabbed_pane, const base::string16& title, View* contents)
     : tabbed_pane_(tabbed_pane),
       title_(new Label(title,
@@ -155,6 +166,10 @@ void Tab::Layout() {
   title_->SetBoundsRect(bounds);
 }
 
+const char* Tab::GetClassName() const {
+  return kViewClassName;
+}
+
 void Tab::SetState(TabState tab_state) {
   if (tab_state == tab_state_)
     return;
@@ -178,6 +193,9 @@ void Tab::SetState(TabState tab_state) {
   SchedulePaint();
 }
 
+// static
+const char TabStrip::kViewClassName[] = "TabStrip";
+
 TabStrip::TabStrip(TabbedPane* tabbed_pane) : tabbed_pane_(tabbed_pane) {}
 
 TabStrip::~TabStrip() {}
@@ -202,6 +220,10 @@ void TabStrip::Layout() {
   }
 }
 
+const char* TabStrip::GetClassName() const {
+  return kViewClassName;
+}
+
 void TabStrip::OnPaint(gfx::Canvas* canvas) {
   OnPaintBackground(canvas);