Rejigger ThemeService: move exposure of ThemeProvider interface to a

chrome/browser/ui/cocoa/gradient_button_cell.mm

Index: chrome/browser/ui/cocoa/gradient_button_cell.mm
diff --git a/chrome/browser/ui/cocoa/gradient_button_cell.mm b/chrome/browser/ui/cocoa/gradient_button_cell.mm
index 74cb77800081d8707f45f0f87c34f121381140cf..a53cbacbfa1732af8275d0f905fb4a4495787558 100644
--- a/chrome/browser/ui/cocoa/gradient_button_cell.mm
+++ b/chrome/browser/ui/cocoa/gradient_button_cell.mm
@@ -604,13 +604,12 @@ static const NSTimeInterval kAnimationContinuousCycleDuration = 0.4;
     CGContextRef context =
         (CGContextRef)([[NSGraphicsContext currentContext] graphicsPort]);
 
-    ThemeService* themeProvider = static_cast<ThemeService*>(
-        [[controlView window] themeProvider]);
+    ui::ThemeProvider* themeProvider = [[controlView window] themeProvider];
     NSColor* color = themeProvider ?
         themeProvider->GetNSColorTint(ThemeProperties::TINT_BUTTONS) :
         [NSColor blackColor];
 
-    if (isTemplate && themeProvider && themeProvider->UsingDefaultTheme()) {
+    if (isTemplate && themeProvider && themeProvider->UsingSystemTheme()) {
       base::scoped_nsobject<NSShadow> shadow([[NSShadow alloc] init]);
       [shadow.get() setShadowColor:themeProvider->GetNSColor(
           ThemeProperties::COLOR_TOOLBAR_BEZEL)];