Add a way to fetch window frame metrics from NativeShellWindow

chrome/browser/ui/extensions/native_shell_window.h

Index: chrome/browser/ui/extensions/native_shell_window.h
diff --git a/chrome/browser/ui/extensions/native_shell_window.h b/chrome/browser/ui/extensions/native_shell_window.h
index 793bf0da7aebd7c1b33889af78e796c222c18926..20ab2f6af023b71dda0db29d2ad1ac98a1b8d444 100644
--- a/chrome/browser/ui/extensions/native_shell_window.h
+++ b/chrome/browser/ui/extensions/native_shell_window.h
@@ -7,6 +7,7 @@
 
 #include "chrome/browser/ui/extensions/shell_window.h"
 #include "chrome/browser/ui/base_window.h"
+#include "ui/gfx/insets.h"
 
 // This is an interface to a native implementation of a shell window, used for
 // new-style packaged apps. Shell windows contain a web contents, but no tabs
@@ -39,6 +40,10 @@ class NativeShellWindow : public BaseWindow {
   // this.
   virtual void RenderViewHostChanged() = 0;
 
+  // Returns the difference between the window bounds (including titlebar and
+  // borders) and the content bounds, if any.
+  virtual gfx::Insets GetFrameInsets() const = 0;
+
   virtual ~NativeShellWindow() {}
 };