Add new SplitString backend.

components/autofill/content/renderer/autofill_agent.cc

Index: components/autofill/content/renderer/autofill_agent.cc
diff --git a/components/autofill/content/renderer/autofill_agent.cc b/components/autofill/content/renderer/autofill_agent.cc
index b6686c3cb5eb678c7b96f121ea07cdef8f133984..b93b00f6d256ad2897223052d792ce001a4f2b77 100644
--- a/components/autofill/content/renderer/autofill_agent.cc
+++ b/components/autofill/content/renderer/autofill_agent.cc
@@ -485,7 +485,8 @@ void AutofillAgent::AcceptDataListSuggestion(
   if (input_element->isMultiple() && input_element->isEmailField()) {
     std::vector<base::string16> parts;
 
-    base::SplitStringDontTrim(input_element->editingValue(), ',', &parts);
+    base::SplitStringDontTrim(
+        base::StringPiece16(input_element->editingValue()), ',', &parts);
     if (parts.size() == 0)
       parts.push_back(base::string16());