Render the tab close button as a vector-based icon.

chrome/browser/ui/views/tabs/tab.h

Index: chrome/browser/ui/views/tabs/tab.h
diff --git a/chrome/browser/ui/views/tabs/tab.h b/chrome/browser/ui/views/tabs/tab.h
index c489362579855c14b2e33e36d4b943fcfe84cc55..23d2a578bb56c5739288e25a7a2b585842b0858b 100644
--- a/chrome/browser/ui/views/tabs/tab.h
+++ b/chrome/browser/ui/views/tabs/tab.h
@@ -196,6 +196,8 @@ class Tab : public gfx::AnimationDelegate,
   bool GetHitTestMask(gfx::Path* mask) const override;
 
   // views::View:
+  void ViewHierarchyChanged(
+      const ViewHierarchyChangedDetails& details) override;
   void OnPaint(gfx::Canvas* canvas) override;
   void Layout() override;
   void OnThemeChanged() override;
@@ -279,6 +281,11 @@ class Tab : public gfx::AnimationDelegate,
   // Returns true if the crash animation is currently running.
   bool IsPerformingCrashAnimation() const;
 
+  // Calculates the correct |close_button_color_| and sets the close button
+  // normal-state image.  This should be called any time the theme or active
+  // state may have changed.
+  void SetCloseButtonNormalStateImage();
+
   // Schedules repaint task for icon.
   void ScheduleIconPaint();