Add base:: namespace to string16 in chrome/browser/extensions.

chrome/browser/extensions/suspicious_extension_bubble_controller.cc

Index: chrome/browser/extensions/suspicious_extension_bubble_controller.cc
diff --git a/chrome/browser/extensions/suspicious_extension_bubble_controller.cc b/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
index 50636ea952e2af594fa9c47bcd47b7f7047531b0..560e4a41cf59cfdbc263f53f750e82d03246a68e 100644
--- a/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
+++ b/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
@@ -122,7 +122,7 @@ GURL SuspiciousExtensionBubbleController::GetLearnMoreUrl() const {
 
 base::string16
 SuspiciousExtensionBubbleController::GetActionButtonLabel() const {
-  return string16();
+  return base::string16();
 }
 
 base::string16
@@ -135,7 +135,7 @@ SuspiciousExtensionBubbleController::ShouldShowExtensionList() const {
   return true;
 }
 
-std::vector<string16>
+std::vector<base::string16>
 SuspiciousExtensionBubbleController::GetExtensions() {
   return GetExtensionList();
 }