remove HEAP from tests

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 272 matching lines @@
  private:
   DISALLOW_COPY_AND_ASSIGN(ConsStringGenerationData);
 };
 
 
 ConsStringGenerationData::ConsStringGenerationData(bool long_blocks,
                                                    Zone* zone) {
   rng_.init();
   InitializeBuildingBlocks(
       building_blocks_, kNumberOfBuildingBlocks, long_blocks, &rng_, zone);
-  empty_string_ = CcTest::i_isolate()->heap()->empty_string();
+  empty_string_ = CcTest::heap()->empty_string();
   Reset();
 }
 
 
 Handle<String> ConsStringGenerationData::block(uint32_t offset) {
   return building_blocks_[offset % kNumberOfBuildingBlocks ];
 }
 
 
 Handle<String> ConsStringGenerationData::block(int offset) {
@@ skipping 1075 matching lines @@
       CheckCanonicalEquivalence(c, test);
       continue;
     }
     if (upper != c && lower != c) {
       CheckCanonicalEquivalence(c, test);
       continue;
     }
     CHECK_EQ(Min(upper, lower), test);
   }
 }