Iterate an array in O(n) rather than O(n^2) time during IDBKey conversion.

content/common/indexed_db/indexed_db_key.cc

Index: content/common/indexed_db/indexed_db_key.cc
diff --git a/content/common/indexed_db/indexed_db_key.cc b/content/common/indexed_db/indexed_db_key.cc
index f2a7cfbb7930b12f47237a7f50d692f925077da6..e55e582dcd1e6e0b2c6fa5d73adbf6120153a58e 100644
--- a/content/common/indexed_db/indexed_db_key.cc
+++ b/content/common/indexed_db/indexed_db_key.cc
@@ -9,6 +9,7 @@
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebVector.h"
 
 using WebKit::WebIDBKey;
+using WebKit::WebVector;
 
 IndexedDBKey::IndexedDBKey()
     : type_(WebIDBKey::NullType),
@@ -55,8 +56,9 @@ void IndexedDBKey::Set(const WebIDBKey& key) {
   type_ = key.type();
   array_.clear();
   if (key.type() == WebIDBKey::ArrayType) {
-    for (size_t i = 0; i < key.array().size(); ++i) {
-      array_.push_back(IndexedDBKey(key.array()[i]));
+    WebVector<WebIDBKey> array = key.array();
+    for (size_t i = 0; i < array.size(); ++i) {
+      array_.push_back(IndexedDBKey(array[i]));
     }
   }
   string_ = key.type() == WebIDBKey::StringType ?