Remove default isolate usage from almost all tests

test/cctest/test-threads.cc

 // Copyright 2008 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 111 matching lines @@
           break;
         }
       }
 
       Thread::YieldCPU();
     } while (true);
   }
 };
 
 
-TEST(JSFunctionResultCachesInTwoThreads) {
+UNINITIALIZED_TEST(JSFunctionResultCachesInTwoThreads) {
   v8::V8::Initialize();
 
   ThreadA threadA;
   ThreadB threadB;
 
   threadA.Start();
   threadB.Start();
 
   threadA.Join();
   threadB.Join();
@@ skipping 63 matching lines @@
     Join();
   }
 };
 
 
 TEST(ThreadJoinSelf) {
   ThreadC thread;
   thread.Start();
   thread.Join();
 }