[Extensions Bindings] Fix native declarativeContent manifest

Fix typo in background.persistent declaration in manifest. This might have
been an issue as its default value is true.

Bug: 750830
Change-Id: I8154bc72bc22bac613494c035951526dfdfcc770
Reviewed-on: https://chromium-review.googlesource.com/599907Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Commit-Queue: Julien Brianceau <jbriance@cisco.com>
Cr-Commit-Position: refs/heads/master@{#491718}

chrome/test/data/extensions/api_test/native_bindings/declarative_content/manifest.json

@@ -6,7 +6,7 @@
   "permissions": ["declarativeContent"],
   "page_action": {},
   "background": {
-    "peristent": false,
+    "persistent": false,
     "scripts": ["background.js"]
   }
 }