Add explicit base namespace to string16 users.

chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc

Index: chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc
diff --git a/chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc b/chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc
index 209be44abc0785ffcfe5e14219a9df5bd3c83a81..2dce164ed14c1b63578bc3cf833a114e437c99c3 100644
--- a/chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc
+++ b/chrome/common/extensions/api/media_galleries_private/media_galleries_handler.cc
@@ -36,7 +36,7 @@ MediaGalleriesHandlerInfo::~MediaGalleriesHandlerInfo() {
 MediaGalleriesHandler* LoadMediaGalleriesHandler(
     const std::string& extension_id,
     const DictionaryValue* media_galleries_handler,
-    string16* error) {
+    base::string16* error) {
   scoped_ptr<MediaGalleriesHandler> result(new MediaGalleriesHandler());
   result->set_extension_id(extension_id);
 
@@ -80,7 +80,7 @@ bool LoadMediaGalleriesHandlers(
     const std::string& extension_id,
     const base::ListValue* extension_actions,
     MediaGalleriesHandler::List* result,
-    string16* error) {
+    base::string16* error) {
   for (base::ListValue::const_iterator iter = extension_actions->begin();
        iter != extension_actions->end();
        ++iter) {
@@ -123,7 +123,7 @@ MediaGalleriesHandlerParser::~MediaGalleriesHandlerParser() {
 }
 
 bool MediaGalleriesHandlerParser::Parse(extensions::Extension* extension,
-                                        string16* error) {
+                                        base::string16* error) {
   const base::ListValue* media_galleries_handlers_value = NULL;
   if (!extension->manifest()->GetList(keys::kMediaGalleriesHandlers,
                                       &media_galleries_handlers_value)) {