VM: Const-correctness fixes.

runtime/vm/dart_api_message.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/dart_api_message.h"
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
 #include "vm/symbols.h"
 #include "vm/unicode.h"
 
@@ skipping 214 matching lines @@
   intptr_t cid = raw->GetClassId();
   switch (cid) {
     case kOneByteStringCid: {
       RawOneByteString* raw_str = reinterpret_cast<RawOneByteString*>(raw);
       const char* str = reinterpret_cast<const char*>(raw_str->ptr()->data());
       ASSERT(str != NULL);
       Dart_CObject* object = NULL;
       for (intptr_t i = 0; i < vm_isolate_references_.length(); i++) {
         object = vm_isolate_references_.At(i);
         if (object->type == Dart_CObject_kString) {
-          if (strcmp(str, const_cast<char*>(object->value.as_string)) == 0) {
+          if (strcmp(str, object->value.as_string) == 0) {
             return object;
           }
         }
       }
       object = CreateDartCObjectString(raw);
       vm_isolate_references_.Add(object);
       return object;
     }
 
     case kMintCid: {
@@ skipping 1091 matching lines @@
     if (!success) {
       UnmarkAllCObjects(object);
       return false;
     }
   }
   UnmarkAllCObjects(object);
   return true;
 }
 
 }  // namespace dart