Add base:: to string16s in chrome/.

chrome/test/automation/tab_proxy.cc

Index: chrome/test/automation/tab_proxy.cc
diff --git a/chrome/test/automation/tab_proxy.cc b/chrome/test/automation/tab_proxy.cc
index f8b6f861a40158f1af0d07245b755ef8c38af029..50d422317ed7a8bdfc61fa90c37a8d82df674b3d 100644
--- a/chrome/test/automation/tab_proxy.cc
+++ b/chrome/test/automation/tab_proxy.cc
@@ -177,7 +177,7 @@ bool TabProxy::ExecuteAndExtractString(const std::wstring& frame_xpath,
   Value* value = NULL;
   bool succeeded = static_cast<ListValue*>(root.get())->Get(0, &value);
   if (succeeded) {
-    string16 read_value;
+    base::string16 read_value;
     succeeded = value->GetAsString(&read_value);
     if (succeeded) {
       // TODO(viettrungluu): remove conversion. (But should |jscript| be UTF-8?)