Convert string16 to base::string16 in content.

content/port/browser/render_widget_host_view_port.h

Index: content/port/browser/render_widget_host_view_port.h
diff --git a/content/port/browser/render_widget_host_view_port.h b/content/port/browser/render_widget_host_view_port.h
index c8774a1c839e07b26ff08d51675992c069864c1b..a668af677451e6d31b75c2a38193cf5bf7c8e59f 100644
--- a/content/port/browser/render_widget_host_view_port.h
+++ b/content/port/browser/render_widget_host_view_port.h
@@ -146,10 +146,10 @@ class CONTENT_EXPORT RenderWidgetHostViewPort : public RenderWidgetHostView,
 
   // Tells the View that the tooltip text for the current mouse position over
   // the page has changed.
-  virtual void SetTooltipText(const string16& tooltip_text) = 0;
+  virtual void SetTooltipText(const base::string16& tooltip_text) = 0;
 
   // Notifies the View that the renderer text selection has changed.
-  virtual void SelectionChanged(const string16& text,
+  virtual void SelectionChanged(const base::string16& text,
                                 size_t offset,
                                 const gfx::Range& range) = 0;