Convert string16 to base::string16 in content.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 66e2e9a136e61923a381cedd69ef59c176fb171e..9b94a443a76053f64499ee169e4c45110b202dbe 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -164,8 +164,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
                            int tag,
                            const gfx::Size& page_size,
                            const gfx::Size& desired_size) OVERRIDE;
-  virtual void Replace(const string16& word) OVERRIDE;
-  virtual void ReplaceMisspelling(const string16& word) OVERRIDE;
+  virtual void Replace(const base::string16& word) OVERRIDE;
+  virtual void ReplaceMisspelling(const base::string16& word) OVERRIDE;
   virtual void ResizeRectChanged(const gfx::Rect& new_rect) OVERRIDE;
   virtual void RestartHangMonitorTimeout() OVERRIDE;
   virtual void SetIgnoreInputEvents(bool ignore_input_events) OVERRIDE;
@@ -333,7 +333,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // * when it receives a "preedit_changed" signal of GtkIMContext (on Linux);
   // * when markedText of NSTextInput is called (on Mac).
   void ImeSetComposition(
-      const string16& text,
+      const base::string16& text,
       const std::vector<blink::WebCompositionUnderline>& underlines,
       int selection_start,
       int selection_end);
@@ -344,7 +344,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   //   (on Windows);
   // * when it receives a "commit" signal of GtkIMContext (on Linux);
   // * when insertText of NSTextInput is called (on Mac).
-  void ImeConfirmComposition(const string16& text,
+  void ImeConfirmComposition(const base::string16& text,
                              const gfx::Range& replacement_range,
                              bool keep_selection);
 
@@ -651,7 +651,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   void OnClose();
   void OnUpdateScreenRectsAck();
   void OnRequestMove(const gfx::Rect& pos);
-  void OnSetTooltipText(const string16& tooltip_text,
+  void OnSetTooltipText(const base::string16& tooltip_text,
                         blink::WebTextDirection text_direction_hint);
   void OnPaintAtSizeAck(int tag, const gfx::Size& size);
 #if defined(OS_MACOSX)