Add explicit base namespace to string16 users.

chrome/common/extensions/api/commands/commands_handler.cc

Index: chrome/common/extensions/api/commands/commands_handler.cc
diff --git a/chrome/common/extensions/api/commands/commands_handler.cc b/chrome/common/extensions/api/commands/commands_handler.cc
index 852f152ab656b693bba4aa3e91769117086ef57e..71697f18e0f7d01ff6e1b72af8acd3e2a4f3b7dc 100644
--- a/chrome/common/extensions/api/commands/commands_handler.cc
+++ b/chrome/common/extensions/api/commands/commands_handler.cc
@@ -61,7 +61,7 @@ CommandsHandler::CommandsHandler() {
 CommandsHandler::~CommandsHandler() {
 }
 
-bool CommandsHandler::Parse(Extension* extension, string16* error) {
+bool CommandsHandler::Parse(Extension* extension, base::string16* error) {
   if (!extension->manifest()->HasKey(keys::kCommands)) {
     scoped_ptr<CommandsInfo> commands_info(new CommandsInfo);
     MaybeSetBrowserActionDefault(extension, commands_info.get());
@@ -139,7 +139,7 @@ void CommandsHandler::MaybeSetBrowserActionDefault(const Extension* extension,
       !info->browser_action_command.get()) {
     info->browser_action_command.reset(
         new Command(manifest_values::kBrowserActionCommandEvent,
-                    string16(),
+                    base::string16(),
                     std::string(),
                     false));
   }