Convert string16 to base::string16 in content.

content/browser/renderer_host/gtk_im_context_wrapper.cc

Index: content/browser/renderer_host/gtk_im_context_wrapper.cc
diff --git a/content/browser/renderer_host/gtk_im_context_wrapper.cc b/content/browser/renderer_host/gtk_im_context_wrapper.cc
index 7ce65585d7b66fc8ca6acd996af01d3dcf8acdd9..d4b77894f5aa254da9296e5811ea05056b2d438b 100644
--- a/content/browser/renderer_host/gtk_im_context_wrapper.cc
+++ b/content/browser/renderer_host/gtk_im_context_wrapper.cc
@@ -477,7 +477,7 @@ void GtkIMContextWrapper::ConfirmComposition() {
     if (host_view_->GetRenderWidgetHost()) {
       RenderWidgetHostImpl::From(
           host_view_->GetRenderWidgetHost())->ImeConfirmComposition(
-              string16(), gfx::Range::InvalidRange(), false);
+              base::string16(), gfx::Range::InvalidRange(), false);
     }
 
     // Reset the input method.
@@ -485,7 +485,7 @@ void GtkIMContextWrapper::ConfirmComposition() {
   }
 }
 
-void GtkIMContextWrapper::HandleCommit(const string16& text) {
+void GtkIMContextWrapper::HandleCommit(const base::string16& text) {
   if (suppress_next_commit_)
     return;