Rework tree APIs to reflect Google style and more const-correctness....

chrome/browser/ui/views/tabs/base_tab.cc

Index: chrome/browser/ui/views/tabs/base_tab.cc
===================================================================
--- chrome/browser/ui/views/tabs/base_tab.cc	(revision 74117)
+++ chrome/browser/ui/views/tabs/base_tab.cc	(working copy)
@@ -58,12 +58,12 @@
   // fire before Enter events, so this works.
   virtual void OnMouseEntered(const views::MouseEvent& event) {
     CustomButton::OnMouseEntered(event);
-    GetParent()->OnMouseEntered(event);
+    parent()->OnMouseEntered(event);
   }
 
   virtual void OnMouseExited(const views::MouseEvent& event) {
     CustomButton::OnMouseExited(event);
-    GetParent()->OnMouseExited(event);
+    parent()->OnMouseExited(event);
   }
 
  private: