cocoa browser: remove remaining non-MD code

chrome/browser/ui/cocoa/background_gradient_view.mm

Index: chrome/browser/ui/cocoa/background_gradient_view.mm
diff --git a/chrome/browser/ui/cocoa/background_gradient_view.mm b/chrome/browser/ui/cocoa/background_gradient_view.mm
index 77318341d6a881a3e872c5360a7fc1977eb81a14..b56f3d0551037bff7704194803f7d524c6c4303e 100644
--- a/chrome/browser/ui/cocoa/background_gradient_view.mm
+++ b/chrome/browser/ui/cocoa/background_gradient_view.mm
@@ -94,16 +94,10 @@ - (NSColor*)strokeColor {
   // anyway).
   if ([window parentWindow])
     window = [window parentWindow];
-  BOOL isActive = [window isMainWindow];
 
   const ui::ThemeProvider* themeProvider = [window themeProvider];
   if (!themeProvider)
     return [NSColor blackColor];
-  if (!ui::MaterialDesignController::IsModeMaterial()) {
-    return themeProvider->GetNSColor(
-        isActive ? ThemeProperties::COLOR_TOOLBAR_STROKE :
-                   ThemeProperties::COLOR_TOOLBAR_STROKE_INACTIVE);
-  }
   return themeProvider->GetNSColor(
              ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR);
 }