Revert of Move JoinString to the base namespace

chrome/browser/search/suggestions/suggestions_source.cc

Index: chrome/browser/search/suggestions/suggestions_source.cc
diff --git a/chrome/browser/search/suggestions/suggestions_source.cc b/chrome/browser/search/suggestions/suggestions_source.cc
index 79ea0be69f6908a7da8da8186ec7c770bfd28f27..486d53dd706bd8078f051005cf2e92f7e2de74e5 100644
--- a/chrome/browser/search/suggestions/suggestions_source.cc
+++ b/chrome/browser/search/suggestions/suggestions_source.cc
@@ -78,7 +78,7 @@
   }
   out.push_back("</ul>");
   out.push_back(kHtmlFooter);
-  *output = base::JoinString(out, base::StringPiece());
+  *output = JoinString(out, "");
 }
 
 // Fills |output| with the HTML needed to display that no suggestions are
@@ -90,7 +90,7 @@
   out.push_back("<h1>Suggestions</h1>\n");
   out.push_back("<p>You have no suggestions.</p>\n");
   out.push_back(kHtmlFooter);
-  *output = base::JoinString(out, base::StringPiece());
+  *output = JoinString(out, "");
 }
 
 }  // namespace