Make assertion scopes thread safe.

test/cctest/test-strings.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 327 matching lines @@
       stats->empty_leaves_++;
       CHECK(!left_is_cons);
     }
     stats->leaves_++;
     stats->chars_ += right_length;
   }
 }
 
 
 void AccumulateStats(Handle<String> cons_string, ConsStringStats* stats) {
-  AssertNoAllocation no_alloc;
+  DisallowHeapAllocation no_allocation;
   if (cons_string->IsConsString()) {
     return AccumulateStats(ConsString::cast(*cons_string), stats);
   }
   // This string got flattened by gc.
   stats->chars_ += cons_string->length();
 }
 
 
 void AccumulateStatsWithOperator(
     ConsString* cons_string, ConsStringStats* stats) {
@@ skipping 304 matching lines @@
     // Build flat version of cons string.
     Handle<String> flat_string = build(i, &data);
     ConsStringStats flat_string_stats;
     AccumulateStats(flat_string, &flat_string_stats);
     // Flatten string.
     FlattenString(flat_string);
     // Build unflattened version of cons string to test.
     Handle<String> cons_string = build(i, &data);
     ConsStringStats cons_string_stats;
     AccumulateStats(cons_string, &cons_string_stats);
-    AssertNoAllocation no_alloc;
+    DisallowHeapAllocation no_allocation;
     PrintStats(data);
     // Full verify of cons string.
     cons_string_stats.VerifyEqual(flat_string_stats);
     cons_string_stats.VerifyEqual(data.stats_);
     VerifyConsString(cons_string, &data);
     String* flat_string_ptr =
         flat_string->IsConsString() ?
         ConsString::cast(*flat_string)->first() :
         *flat_string;
     VerifyCharacterStream(flat_string_ptr, *cons_string);
@@ skipping 653 matching lines @@
       CheckCanonicalEquivalence(c, test);
       continue;
     }
     if (upper != c && lower != c) {
       CheckCanonicalEquivalence(c, test);
       continue;
     }
     CHECK_EQ(Min(upper, lower), test);
   }
 }