[Mac] Increase contrast of toolbar button hover bg in MD Incognito.

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

Index: chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm b/chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm
index e0726749932e1ff59d7655f05cf9be3780182e1e..3c22955f6c63c8e711909c50749dcf0808190ac3 100644
--- a/chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm
+++ b/chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.mm
@@ -90,13 +90,13 @@ const NSSize kMDButtonIconSize = NSMakeSize(16, 16);
       fillColor = [NSColor colorWithCalibratedWhite:0 alpha:0.08];
       break;
     case ToolbarButtonImageBackgroundStyle::HOVER_THEMED:
-      fillColor = [NSColor colorWithCalibratedWhite:1 alpha:0.08];
+      fillColor = [NSColor colorWithCalibratedWhite:1 alpha:0.12];
       break;
     case ToolbarButtonImageBackgroundStyle::PRESSED:
       fillColor = [NSColor colorWithCalibratedWhite:0 alpha:0.12];
       break;
     case ToolbarButtonImageBackgroundStyle::PRESSED_THEMED:
-      fillColor = [NSColor colorWithCalibratedWhite:1 alpha:0.12];
+      fillColor = [NSColor colorWithCalibratedWhite:1 alpha:0.16];
       break;
   }