[runtime] Remove the obsolete %_StringCharAt intrinsic.

test/cctest/compiler/test-run-intrinsics.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/cctest/compiler/function-tester.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 133 matching lines @@
 
 TEST(StringAdd) {
   FunctionTester T("(function(a,b) { return %_StringAdd(a,b); })", flags);
 
   T.CheckCall(T.Val("aaabbb"), T.Val("aaa"), T.Val("bbb"));
   T.CheckCall(T.Val("aaa"), T.Val("aaa"), T.Val(""));
   T.CheckCall(T.Val("bbb"), T.Val(""), T.Val("bbb"));
 }
 
 
-TEST(StringCharAt) {
-  FunctionTester T("(function(a,b) { return %_StringCharAt(a,b); })", flags);
-
-  T.CheckCall(T.Val("e"), T.Val("huge fan!"), T.Val(3));
-  T.CheckCall(T.Val("f"), T.Val("\xE2\x9D\x8A fan!"), T.Val(2));
-  T.CheckCall(T.Val(""), T.Val("not a fan!"), T.Val(23));
-}
-
-
 TEST(StringCharCodeAt) {
   FunctionTester T("(function(a,b) { return %_StringCharCodeAt(a,b); })",
                    flags);
 
   T.CheckCall(T.Val('e'), T.Val("huge fan!"), T.Val(3));
   T.CheckCall(T.Val('f'), T.Val("\xE2\x9D\x8A fan!"), T.Val(2));
   T.CheckCall(T.nan(), T.Val("not a fan!"), T.Val(23));
 }
 
 
@@ skipping 60 matching lines @@
 
   T.CheckCall(T.Val("a"), T.Val("a"));
   T.CheckCall(T.Val("b"), T.NewObject("(new String('b'))"));
   T.CheckCall(T.Val(123), T.Val(123));
   T.CheckCall(T.Val(456), T.NewObject("(new Number(456))"));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8