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 7406536df1779d07b7685ef43abe8a8d5de44506..ca4c881f17815979526197b2c3e17bf03ff5a860 100644
--- a/chrome/browser/ui/extensions/shell_window.cc
+++ b/chrome/browser/ui/extensions/shell_window.cc
@@ -287,10 +287,14 @@ void ShellWindow::OnNativeClose() {
   delete this;
 }
 
-BaseWindow* ShellWindow::GetBaseWindow() {
+NativeShellWindow* ShellWindow::GetBaseWindow() {
   return native_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