Add vdc checkpoint restoreCheckpointPart

Restores the first n entries of a checkpoint. Allows automated testing
of interrupted restores.

Test: vdc checkpoint restoreCheckpoint [device] [n]
Change-Id: I47570e8eba0bc3c6549a04a33600df05d393990b
diff --git a/VoldNativeService.cpp b/VoldNativeService.cpp
index 1001d2b..69f8a8c 100644
--- a/VoldNativeService.cpp
+++ b/VoldNativeService.cpp
@@ -850,6 +850,14 @@
     return cp_restoreCheckpoint(mountPoint);
 }
 
+binder::Status VoldNativeService::restoreCheckpointPart(const std::string& mountPoint, int count) {
+    ENFORCE_UID(AID_SYSTEM);
+    CHECK_ARGUMENT_PATH(mountPoint);
+    ACQUIRE_LOCK;
+
+    return cp_restoreCheckpoint(mountPoint, count);
+}
+
 binder::Status VoldNativeService::markBootAttempt() {
     ENFORCE_UID(AID_SYSTEM);
     ACQUIRE_LOCK;