Fix test timeout; faster DEBUG String::CharAt by not using mutable accessor.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 17022 matching lines @@
 
 
 intptr_t String::Hash(const int32_t* characters, intptr_t len) {
   return HashImpl(characters, len);
 }
 
 
 uint16_t String::CharAt(intptr_t index) const {
   intptr_t class_id = raw()->GetClassId();
   ASSERT(RawObject::IsStringClassId(class_id));
-  NoGCScope no_gc;
   if (class_id == kOneByteStringCid) {
-    return *OneByteString::CharAddr(*this, index);
+    return OneByteString::CharAt(*this, index);
   }
   if (class_id == kTwoByteStringCid) {
-    return *TwoByteString::CharAddr(*this, index);
+    return TwoByteString::CharAt(*this, index);
   }
   if (class_id == kExternalOneByteStringCid) {
-    return *ExternalOneByteString::CharAddr(*this, index);
+    return ExternalOneByteString::CharAt(*this, index);
   }
   ASSERT(class_id == kExternalTwoByteStringCid);
-  return *ExternalTwoByteString::CharAddr(*this, index);
+  return ExternalTwoByteString::CharAt(*this, index);
 }
 
 
 Scanner::CharAtFunc String::CharAtFunc() const {
   intptr_t class_id = raw()->GetClassId();
   ASSERT(RawObject::IsStringClassId(class_id));
   if (class_id == kOneByteStringCid) {
     return &OneByteString::CharAt;
   }
   if (class_id == kTwoByteStringCid) {
@@ skipping 3253 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart