diff --git a/services/sync/modules/util.js b/services/sync/modules/util.js
index 44245919b010..1c8f3079bb00 100644
--- a/services/sync/modules/util.js
+++ b/services/sync/modules/util.js
@@ -249,6 +249,24 @@ let Utils = {
     return Utils.waitForSyncCallback(storageCallback.syncCb);
   },
 
+  /*
+   * Partition the input array into an array of arrays. Return a generator.
+   */
+  slices: function slices(arr, sliceSize) {
+    if (!sliceSize || sliceSize <= 0)
+      throw "Invalid slice size.";
+
+    if (sliceSize > arr.length) {
+      yield arr;
+    } else {
+      let offset = 0;
+      while (arr.length > offset) {
+        yield arr.slice(offset, offset + sliceSize);
+        offset += sliceSize;
+      }
+    }
+  },
+
   byteArrayToString: function byteArrayToString(bytes) {
     return [String.fromCharCode(byte) for each (byte in bytes)].join("");
   },
diff --git a/services/sync/tests/unit/test_utils_slices.js b/services/sync/tests/unit/test_utils_slices.js
new file mode 100644
index 000000000000..7493e329043f
--- /dev/null
+++ b/services/sync/tests/unit/test_utils_slices.js
@@ -0,0 +1,48 @@
+Cu.import("resource://services-sync/util.js");
+
+function run_test() {
+  let input = [1, 2, 3, 4, 5];
+
+  let err;
+  try {
+    Utils.slices(input, 0).next();
+  } catch (ex) {
+    err = ex;
+  }
+  do_check_eq("Invalid slice size.", err);
+
+  err = undefined;
+  try {
+    Utils.slices(input).next();
+  } catch (ex) {
+    err = ex;
+  }
+  do_check_eq("Invalid slice size.", err);
+
+  function slurp(g) [x for each (x in g)]
+
+  let sliced1 = slurp(Utils.slices(input, 1));
+  let sliced2 = slurp(Utils.slices(input, 2));
+  let sliced3 = slurp(Utils.slices(input, 5));
+  let sliced4 = slurp(Utils.slices(input, 7));
+
+  do_check_eq(sliced1.length, 5);
+  do_check_eq(sliced2.length, 3);
+  do_check_eq(sliced3.length, 1);
+  do_check_eq(sliced4.length, 1);
+  sliced1.every(function(x) x.length == 1);
+  _(JSON.stringify(sliced2));
+  do_check_eq(sliced2[0].length, 2);
+  do_check_eq(sliced2[1].length, 2);
+  do_check_eq(sliced2[2].length, 1);
+  sliced3.every(function(x) x.length == 5);
+  sliced4.every(function(x) x.length == 5);
+
+  let sliced5 = slurp(Utils.slices(["foo"], 50));
+  do_check_eq(sliced5.length, 1);
+  do_check_eq(sliced5[0], "foo");
+
+  let sliced6 = slurp(Utils.slices([], 50));
+  do_check_eq(sliced6.length, 1);
+  do_check_eq(sliced6[0].length, 0);
+}
diff --git a/services/sync/tests/unit/xpcshell.ini b/services/sync/tests/unit/xpcshell.ini
index a97e35228e94..e2a1405d5850 100644
--- a/services/sync/tests/unit/xpcshell.ini
+++ b/services/sync/tests/unit/xpcshell.ini
@@ -97,5 +97,6 @@ tail =
 [test_utils_sha1.js]
 [test_utils_sha1hmac.js]
 [test_utils_sha256HMAC.js]
+[test_utils_slices.js]
 [test_utils_stackTrace.js]
 [test_utils_utf8.js]