cocoa browser: remove non-material toolbar support

chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm

Index: chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm b/chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm
index 82283f02d9843fbb61f895f78bd0ff85d6c96d98..5e4f5c0e849d9e70dad51792e3b69c51cfd4df9f 100644
--- a/chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm
+++ b/chrome/browser/ui/cocoa/toolbar/toolbar_view_cocoa.mm
@@ -21,15 +21,6 @@ - (void)drawRect:(NSRect)dirtyRect {
   [self drawBackground:dirtyRect];
 }
 
-// Override of |-[BackgroundGradientView strokeColor]|; make it respect opacity.
-- (NSColor*)strokeColor {
-  // Only return a transparent color if not Material Design.
-  if (!ui::MaterialDesignController::IsModeMaterial()) {
-    return [[super strokeColor] colorWithAlphaComponent:[self dividerOpacity]];
-  }
-  return [super strokeColor];
-}
-
 - (BOOL)accessibilityIsIgnored {
   return NO;
 }