Convert string16 to base::string16 in content.

content/child/indexed_db/indexed_db_key_builders.cc

Index: content/child/indexed_db/indexed_db_key_builders.cc
diff --git a/content/child/indexed_db/indexed_db_key_builders.cc b/content/child/indexed_db/indexed_db_key_builders.cc
index a17065f4e9fc18b881242e47aafaffc969afb016..ed84ac41c2c174eabb1f2340645150b4c16d092a 100644
--- a/content/child/indexed_db/indexed_db_key_builders.cc
+++ b/content/child/indexed_db/indexed_db_key_builders.cc
@@ -30,9 +30,9 @@ static content::IndexedDBKey::KeyArray CopyKeyArray(const WebIDBKey& other) {
   return result;
 }
 
-static std::vector<string16> CopyArray(
+static std::vector<base::string16> CopyArray(
     const WebVector<WebString>& array) {
-  std::vector<string16> copy(array.size());
+  std::vector<base::string16> copy(array.size());
   for (size_t i = 0; i < array.size(); ++i)
     copy[i] = array[i];
   return copy;