Add base:: to straggling string16 in content/.

content/shell/renderer/test_runner/WebTestProxy.cpp

Index: content/shell/renderer/test_runner/WebTestProxy.cpp
diff --git a/content/shell/renderer/test_runner/WebTestProxy.cpp b/content/shell/renderer/test_runner/WebTestProxy.cpp
index 541ec746f03ae7ab447bbba9d678591820c8fcda..f6cec531470a6a76378c5587978c2fd525aa4959 100644
--- a/content/shell/renderer/test_runner/WebTestProxy.cpp
+++ b/content/shell/renderer/test_runner/WebTestProxy.cpp
@@ -297,8 +297,8 @@ 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;