Add an isCheckpointing() binder call for adb remount.

This is needed so "adb remount" can avoid writing to /data during a
checkpoint.

Bug: 157540389
Test: manual test
Change-Id: I33a691da3b99343acfc1e8ddf68a14504c3bfbe1
Merged-In: I33a691da3b99343acfc1e8ddf68a14504c3bfbe1
diff --git a/VoldNativeService.cpp b/VoldNativeService.cpp
index a37ba5a..0cb86ce 100644
--- a/VoldNativeService.cpp
+++ b/VoldNativeService.cpp
@@ -809,6 +809,14 @@
     return Ok();
 }
 
+binder::Status VoldNativeService::isCheckpointing(bool* _aidl_return) {
+    ENFORCE_SYSTEM_OR_ROOT;
+    ACQUIRE_LOCK;
+
+    *_aidl_return = cp_isCheckpointing();
+    return Ok();
+}
+
 binder::Status VoldNativeService::commitChanges() {
     ENFORCE_SYSTEM_OR_ROOT;
     ACQUIRE_LOCK;