[builtins] Migrate String.prototype.charCodeAt and String.prototype.charAt to TurboFan.

src/js/messages.js

Index: src/js/messages.js
diff --git a/src/js/messages.js b/src/js/messages.js
index f8cb967cdd064238ebbe75bf50edc2be168271f6..69d3fbb4f50c89cc03b0ee80c9c1abe7a53997ac 100644
--- a/src/js/messages.js
+++ b/src/js/messages.js
@@ -37,7 +37,6 @@ var ObjectHasOwnProperty;
 var ObjectToString = utils.ImportNow("object_to_string");
 var Script = utils.ImportNow("Script");
 var stackTraceSymbol = utils.ImportNow("stack_trace_symbol");
-var StringCharAt;
 var StringIndexOf;
 var StringSubstring;
 var SymbolToString;
@@ -57,7 +56,6 @@ utils.Import(function(from) {
   Int8x16ToString = from.Int8x16ToString;
   ObjectDefineProperty = from.ObjectDefineProperty;
   ObjectHasOwnProperty = from.ObjectHasOwnProperty;
-  StringCharAt = from.StringCharAt;
   StringIndexOf = from.StringIndexOf;
   StringSubstring = from.StringSubstring;
   SymbolToString = from.SymbolToString;
@@ -255,6 +253,7 @@ function ScriptLineFromPosition(position) {
   return -1;
 }
 
+
 /**
  * Get information on a specific source position.
  * @param {number} position The source position
@@ -272,7 +271,7 @@ function ScriptLocationFromPosition(position,
   var line_ends = this.line_ends;
   var start = line == 0 ? 0 : line_ends[line - 1] + 1;
   var end = line_ends[line];
-  if (end > 0 && %_Call(StringCharAt, this.source, end - 1) == '\r') {
+  if (end > 0 && %_StringCharAt(this.source, end - 1) === '\r') {
     end--;
   }
   var column = position - start;