Rename and simplify DropPermissionHolder

Rename DropPermissionHolder to DropPermissions and move
all server-side implementation details into a separate class.
Rename DragEvent.getDropPermissionHolder to
requestDropPermissions and make it take the permissions
implicitly.

Change-Id: Ia83f7cb8af07ce13ba9536d24b0f9d63331d8736
diff --git a/Android.mk b/Android.mk
index 137ef85..a098379 100644
--- a/Android.mk
+++ b/Android.mk
@@ -308,7 +308,7 @@
 	core/java/com/android/internal/textservice/ISpellCheckerSessionListener.aidl \
 	core/java/com/android/internal/textservice/ITextServicesManager.aidl \
 	core/java/com/android/internal/textservice/ITextServicesSessionListener.aidl \
-	core/java/com/android/internal/view/IDropPermissionHolder.aidl \
+	core/java/com/android/internal/view/IDropPermissions.aidl \
 	core/java/com/android/internal/view/IInputContext.aidl \
 	core/java/com/android/internal/view/IInputContextCallback.aidl \
 	core/java/com/android/internal/view/IInputMethod.aidl \