Replace string16 with base::string16.

chrome/browser/background/background_mode_manager_unittest.cc

Index: chrome/browser/background/background_mode_manager_unittest.cc
diff --git a/chrome/browser/background/background_mode_manager_unittest.cc b/chrome/browser/background/background_mode_manager_unittest.cc
index 3e0e3524cd3d31c9b058700713ae4ea8689db775..9eb09d2d62e932b7cba35b5c4b9eef6a3589a30a 100644
--- a/chrome/browser/background/background_mode_manager_unittest.cc
+++ b/chrome/browser/background/background_mode_manager_unittest.cc
@@ -120,10 +120,10 @@ class TestBackgroundModeManager : public BackgroundModeManager {
 class TestStatusIcon : public StatusIcon {
   virtual void SetImage(const gfx::ImageSkia& image) OVERRIDE {}
   virtual void SetPressedImage(const gfx::ImageSkia& image) OVERRIDE {}
-  virtual void SetToolTip(const string16& tool_tip) OVERRIDE {}
+  virtual void SetToolTip(const base::string16& tool_tip) OVERRIDE {}
   virtual void DisplayBalloon(const gfx::ImageSkia& icon,
-                              const string16& title,
-                              const string16& contents) OVERRIDE {}
+                              const base::string16& title,
+                              const base::string16& contents) OVERRIDE {}
   virtual void UpdatePlatformContextMenu(
       StatusIconMenuModel* menu) OVERRIDE {}
 };