mash: Change CastConfigDelegate to a mojoified CastConfigClient.

ash/common/wm_shell.h

Index: ash/common/wm_shell.h
diff --git a/ash/common/wm_shell.h b/ash/common/wm_shell.h
index b7adf68b69edb12a1230eb3f5a131ec648ae1cdd..dd7de8181cd33a4f2b10300fc56cebf23d01c9b3 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -44,6 +44,7 @@ namespace ash {
 class AcceleratorController;
 class AccessibilityDelegate;
 class BrightnessControlDelegate;
+class CastConfigClientProxy;
 class FocusCycler;
 class ImmersiveContextAsh;
 class ImmersiveFullscreenController;
@@ -122,6 +123,10 @@ class ASH_EXPORT WmShell {
     return brightness_control_delegate_.get();
   }
 
+  CastConfigClientProxy* cast_config_client() {
+    return cast_config_client_.get();
+  }
+
   FocusCycler* focus_cycler() { return focus_cycler_.get(); }
 
   KeyboardBrightnessControlDelegate* keyboard_brightness_control_delegate() {
@@ -479,6 +484,7 @@ class ASH_EXPORT WmShell {
   std::unique_ptr<AcceleratorController> accelerator_controller_;
   std::unique_ptr<AccessibilityDelegate> accessibility_delegate_;
   std::unique_ptr<BrightnessControlDelegate> brightness_control_delegate_;
+  std::unique_ptr<CastConfigClientProxy> cast_config_client_;
   std::unique_ptr<FocusCycler> focus_cycler_;
   std::unique_ptr<ImmersiveContextAsh> immersive_context_;
   std::unique_ptr<KeyboardBrightnessControlDelegate>