Simplify implementation of Mutex.

test/cctest/test-platform-nullos.cc

 // Copyright 2006-2008 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 34 matching lines @@
 
 static const int kLockCounterLimit = 50;
 static int busy_lock_counter = 0;
 
 
 static void LoopIncrement(Mutex* mutex, int rem) {
   while (true) {
     int count = 0;
     int last_count = -1;
     do {
-      CHECK_EQ(0, mutex->Lock());
+      mutex->Lock();
       count = busy_lock_counter;
-      CHECK_EQ(0, mutex->Unlock());
+      mutex->Unlock();
       yield();
     } while (count % 2 == rem && count < kLockCounterLimit);
     if (count >= kLockCounterLimit) break;
-    CHECK_EQ(0, mutex->Lock());
+    mutex->Lock();
     CHECK_EQ(count, busy_lock_counter);
     CHECK(last_count == -1 || count == last_count + 1);
     busy_lock_counter++;
     last_count = count;
-    CHECK_EQ(0, mutex->Unlock());
+    mutex->Unlock();
     yield();
   }
 }
 
 
 static void* RunTestBusyLock(void* arg) {
   LoopIncrement(static_cast<Mutex*>(arg), 0);
   return 0;
 }
 
@@ skipping 19 matching lines @@
   CHECK(vm->IsReserved());
   void* block_addr = vm->address();
   size_t block_size = 4 * KB;
   CHECK(vm->Commit(block_addr, block_size, false));
   // Check whether we can write to memory.
   int* addr = static_cast<int*>(block_addr);
   addr[KB-1] = 2;
   CHECK(vm->Uncommit(block_addr, block_size));
   delete vm;
 }