Convert CancelationOptions::Mode to an enum class.

C++11 offers better type-safety, we should use it.

Test: compiles
Change-Id: Ied8edcabf2c2a0c9f52c7077e45228c72134e330
diff --git a/services/inputflinger/dispatcher/CancelationOptions.h b/services/inputflinger/dispatcher/CancelationOptions.h
index d210e9e..512cb6e 100644
--- a/services/inputflinger/dispatcher/CancelationOptions.h
+++ b/services/inputflinger/dispatcher/CancelationOptions.h
@@ -24,7 +24,7 @@
 
 /* Specifies which events are to be canceled and why. */
 struct CancelationOptions {
-    enum Mode {
+    enum class Mode {
         CANCEL_ALL_EVENTS = 0,
         CANCEL_POINTER_EVENTS = 1,
         CANCEL_NON_POINTER_EVENTS = 2,