Prefix string16 with base:: in ui/.

ui/views/controls/progress_bar.cc

Index: ui/views/controls/progress_bar.cc
diff --git a/ui/views/controls/progress_bar.cc b/ui/views/controls/progress_bar.cc
index 087c2df9830910322cb1a83ef16514253a69c2c3..1b6bba05f15fb62d8620d3dcaaa64a67223c5d3b 100644
--- a/ui/views/controls/progress_bar.cc
+++ b/ui/views/controls/progress_bar.cc
@@ -167,11 +167,12 @@ void ProgressBar::SetValue(double value) {
   }
 }
 
-void ProgressBar::SetTooltipText(const string16& tooltip_text) {
+void ProgressBar::SetTooltipText(const base::string16& tooltip_text) {
   tooltip_text_ = tooltip_text;
 }
 
-bool ProgressBar::GetTooltipText(const gfx::Point& p, string16* tooltip) const {
+bool ProgressBar::GetTooltipText(const gfx::Point& p,
+                                 base::string16* tooltip) const {
   DCHECK(tooltip);
   *tooltip = tooltip_text_;
   return !tooltip_text_.empty();