Force databases and localstorage to be enabled extensions.

chrome/test/data/extensions/api_test/storage/background.html

+<script>
+  // store some stuff in local storage
+  localStorage.foo = "bar";
+  
+  // store some stuff in a database
+  var db = window.openDatabase("mydb2", "1.0", "database test");
+  db.transaction(function(tx) {
+    tx.executeSql("drop table if exists note");
+    tx.executeSql("create table note (body text)", []);
+    tx.executeSql("insert into note values ('hotdog')", []);
+  }, function(error) {
+    fail(error.message);
+  });
+
+  // Open a tab. This doesn't really prove we're writing to disk, but it is
+  // difficult to prove that without shutting down the process. We'll just
+  // trust that if this next trick works, that the real testing for local
+  // storage is good enough to catch more subtle errors.
+  chrome.tabs.create({
+    url: "tab.html"
+  });
+</script>