Proper rendering of stacked tabs for MD.

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

Index: chrome/browser/ui/views/tabs/tab_controller.h
diff --git a/chrome/browser/ui/views/tabs/tab_controller.h b/chrome/browser/ui/views/tabs/tab_controller.h
index 90d0d0d3670bfb4a0770f2e56eb5f4a95411061a..88e61a1847aeb997c3f689c6d99f958a013abbf3 100644
--- a/chrome/browser/ui/views/tabs/tab_controller.h
+++ b/chrome/browser/ui/views/tabs/tab_controller.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_UI_VIEWS_TABS_TAB_CONTROLLER_H_
 #define CHROME_BROWSER_UI_VIEWS_TABS_TAB_CONTROLLER_H_
 
+#include "base/callback_forward.h"
 #include "chrome/browser/ui/views/tabs/tab_strip_types.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/ui_base_types.h"
@@ -12,6 +13,7 @@
 class Tab;
 
 namespace gfx {
+class Path;
 class Point;
 class Size;
 }
@@ -37,6 +39,9 @@ class TabController {
   // to be hidden.
   virtual bool ShouldHideCloseButtonForInactiveTabs() = 0;
 
+  // Returns true if ShouldPaintTab() could return a non-empty clip path.
+  virtual bool MaySetClip() = 0;
+
   // Selects the tab.
   virtual void SelectTab(Tab* tab) = 0;
 
@@ -92,10 +97,16 @@ class TabController {
   virtual void OnMouseEventInTab(views::View* source,
                                  const ui::MouseEvent& event) = 0;
 
-  // Returns true if |tab| needs to be painted. If false is returned the tab is
-  // not painted. If true is returned the tab should be painted and |clip| is
-  // set to the clip (if |clip| is empty means no clip).
-  virtual bool ShouldPaintTab(const Tab* tab, gfx::Rect* clip) = 0;
+  // Returns whether |tab| needs to be painted. When this returns true, |clip|
+  // is set to the path which should be clipped out of the current tab's region
+  // (for hit testing or painting), if any.  |clip| is only non-empty when
+  // stacking tabs; if it is empty, no clipping is needed.  |border_callback| is
+  // a callback which returns a tab's border given its size, and is used in
+  // computing |clip|.
+  virtual bool ShouldPaintTab(
+      const Tab* tab,
+      const base::Callback<gfx::Path(const gfx::Size&)>& border_callback,
+      gfx::Path* clip) = 0;
 
   // Returns true if tab loading throbbers can be painted to a composited layer.
   // This can only be done when the TabController can guarantee that nothing