Convert string16 to base::string16 in content.

content/browser/renderer_host/render_widget_host_view_android.cc

Index: content/browser/renderer_host/render_widget_host_view_android.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_android.cc b/content/browser/renderer_host/render_widget_host_view_android.cc
index c8c559bc5edadb67bfe094bdfb535a46e5c15901..0c79dbd35c98006223abbfbb6a97a0edac360b48 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -524,11 +524,11 @@ void RenderWidgetHostViewAndroid::Destroy() {
 }
 
 void RenderWidgetHostViewAndroid::SetTooltipText(
-    const string16& tooltip_text) {
+    const base::string16& tooltip_text) {
   // Tooltips don't makes sense on Android.
 }
 
-void RenderWidgetHostViewAndroid::SelectionChanged(const string16& text,
+void RenderWidgetHostViewAndroid::SelectionChanged(const base::string16& text,
                                                    size_t offset,
                                                    const gfx::Range& range) {
   RenderWidgetHostViewBase::SelectionChanged(text, offset, range);