mus: Introduce high-contrast mode in mus.

ash/mus/manifest.json

Index: ash/mus/manifest.json
diff --git a/ash/mus/manifest.json b/ash/mus/manifest.json
index d2bfcf6f50d31dda17be7dfb5ca60d5b4a88ce41..8e59700881d62494a6fa5fca5f5f0f556c165470 100644
--- a/ash/mus/manifest.json
+++ b/ash/mus/manifest.json
@@ -7,7 +7,7 @@
       "mus:window_manager" : [ "ui::mojom::AcceleratorRegistrar" ]
     },
     "required": {
-      "*": { "classes": [ "app" ] },
+      "*": { "classes": [ "accessibility", "app" ] },

[msw, 2016/07/12 18:30:09]

Wouldn't it make more sense to list ui::mojom::AccessibilityManager in the
interfaces required of mojo:ui instead? Will we soon add other interfaces to the
accessibility 'class'?

[sadrul, 2016/07/13 01:01:22]

I expect we will add additional interfaces for accessibility. Although it's not
clear if we will connect to those via shell, or if AccessibilityManager will
provide those impls. Removed the 'accessibility' class from this CL.

       "mojo:ui": { "interfaces": [ "ui::mojom::WindowManagerWindowTreeFactory" ] }
     }
   }