Add NULL check for NativeTheme in scrollbar methods. A NULL theme can

happen with some code paths.

BUG=175600
TEST=none
R=sadrul@chromium.org


Review URL: https://chromiumcodereview.appspot.com/12212144

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182142 0039d316-1c4b-4281-b951-d872f2087c98

ui/views/controls/scrollbar/native_scroll_bar_views.cc

@@ -382,6 +382,8 @@ NativeScrollBarWrapper* NativeScrollBarWrapper::CreateWrapper(
 // static
 int NativeScrollBarWrapper::GetHorizontalScrollBarHeight(
     const ui::NativeTheme* theme) {
+  if (!theme)
+    theme = ui::NativeTheme::instance();
   ui::NativeTheme::ExtraParams button_params;
   button_params.scrollbar_arrow.is_hovering = false;
   gfx::Size button_size = theme->GetPartSize(
@@ -402,6 +404,8 @@ int NativeScrollBarWrapper::GetHorizontalScrollBarHeight(
 // static
 int NativeScrollBarWrapper::GetVerticalScrollBarWidth(
     const ui::NativeTheme* theme) {
+  if (!theme)
+    theme = ui::NativeTheme::instance();
   ui::NativeTheme::ExtraParams button_params;
   button_params.scrollbar_arrow.is_hovering = false;
   gfx::Size button_size = theme->GetPartSize(