Add a way to fetch window frame metrics from NativeShellWindow

chrome/browser/ui/extensions/shell_window.cc

Index: chrome/browser/ui/extensions/shell_window.cc
diff --git a/chrome/browser/ui/extensions/shell_window.cc b/chrome/browser/ui/extensions/shell_window.cc
index 8176073872681cc31e6ffcfb6da49cfb534099f3..0a7d23fadd592fa5f4d15d9cf656205750979143 100644
--- a/chrome/browser/ui/extensions/shell_window.cc
+++ b/chrome/browser/ui/extensions/shell_window.cc
@@ -351,11 +351,14 @@ void ShellWindow::OnNativeWindowChanged() {
                                            false));
 }
 
-
-BaseWindow* ShellWindow::GetBaseWindow() {
+NativeAppWindow* ShellWindow::GetBaseWindow() {
   return native_app_window_.get();
 }
 
+gfx::NativeWindow ShellWindow::GetNativeWindow() {
+  return GetBaseWindow()->GetNativeWindow();
+}
+
 string16 ShellWindow::GetTitle() const {
   // WebContents::GetTitle() will return the page's URL if there's no <title>
   // specified. However, we'd prefer to show the name of the extension in that