Fix spelling in DOM Storage test.

content/test/data/dom_storage/verify_data.html

Index: content/test/data/dom_storage/verify_data.html
diff --git a/content/test/data/dom_storage/verify_data.html b/content/test/data/dom_storage/verify_data.html
index cc845bb86a6a8af5ad0e499b629c1cadea47f88e..6349b04b1eb02140a516d2412cbf308bf6ba94d8 100644
--- a/content/test/data/dom_storage/verify_data.html
+++ b/content/test/data/dom_storage/verify_data.html
@@ -5,7 +5,7 @@
 function test() {
   let val = window.localStorage['foo'];
   if (val !== 'bar')
-    fail('Read incorrect value from localStorage. Excpected "bar", got "' + val + '"');
+    fail('Read incorrect value from localStorage. Expected "bar", got "' + val + '"');
   else
     done();
 }