Add base:: to string16 in Source/testing/runner/.

Source/testing/runner/WebTestProxy.cpp

Index: Source/testing/runner/WebTestProxy.cpp
diff --git a/Source/testing/runner/WebTestProxy.cpp b/Source/testing/runner/WebTestProxy.cpp
index 8224389f17d4ba336bcd3778cfd95dbdf35adf31..4e6fdea45a256d07e808977482b5b0eb91017577 100644
--- a/Source/testing/runner/WebTestProxy.cpp
+++ b/Source/testing/runner/WebTestProxy.cpp
@@ -323,8 +323,8 @@ struct ToLower {
 // Returns True if item1 < item2.
 bool HistoryItemCompareLess(const WebHistoryItem& item1, const WebHistoryItem& item2)
 {
-    string16 target1 = item1.target();
-    string16 target2 = item2.target();
+    base::string16 target1 = item1.target();
+    base::string16 target2 = item2.target();
     std::transform(target1.begin(), target1.end(), target1.begin(), ToLower());
     std::transform(target2.begin(), target2.end(), target2.begin(), ToLower());
     return target1 < target2;