Rejigger ThemeService: move exposure of ThemeProvider interface to a

chrome/browser/ui/cocoa/tabs/tab_view.mm

Index: chrome/browser/ui/cocoa/tabs/tab_view.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_view.mm b/chrome/browser/ui/cocoa/tabs/tab_view.mm
index 1e4d21d6df8c79e216795eb2492a3dd32106c407..0bc667906bc16ad5d42f2436c6dd68acf8e3bf58 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_view.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_view.mm
@@ -277,8 +277,7 @@ ui::ThreePartImage& GetStrokeImage(bool active) {
 // Returns the color used to draw the background of a tab. |selected| selects
 // between the foreground and background tabs.
 - (NSColor*)backgroundColorForSelected:(bool)selected {
-  ThemeService* themeProvider =
-      static_cast<ThemeService*>([[self window] themeProvider]);
+  ui::ThemeProvider* themeProvider = [[self window] themeProvider];
   if (!themeProvider)
     return [[self window] backgroundColor];
 
@@ -298,7 +297,7 @@ ui::ThreePartImage& GetStrokeImage(bool active) {
   // Themes don't have an inactive image so only look for one if there's no
   // theme.
   bool active =
-      [[self window] isMainWindow] || !themeProvider->UsingDefaultTheme();
+      [[self window] isMainWindow] || !themeProvider->UsingSystemTheme();
   return themeProvider->GetNSImageColorNamed(bitmapResources[active][selected]);
 }