Fix more -Wsign-compare bugs with GCC 4.9.2.

test/cctest/test-heap.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 5768 matching lines @@
   Isolate* isolate = CcTest::i_isolate();
   Heap* heap = isolate->heap();
   size_t counter1 = heap->NewSpaceAllocationCounter();
   heap->CollectGarbage(NEW_SPACE);
   const size_t kSize = 1024;
   AllocateInSpace(isolate, kSize, NEW_SPACE);
   size_t counter2 = heap->NewSpaceAllocationCounter();
   CHECK_EQ(kSize, counter2 - counter1);
   heap->CollectGarbage(NEW_SPACE);
   size_t counter3 = heap->NewSpaceAllocationCounter();
-  CHECK_EQ(0, counter3 - counter2);
+  CHECK_EQ(0U, counter3 - counter2);
   // Test counter overflow.
   size_t max_counter = -1;
   heap->set_new_space_allocation_counter(max_counter - 10 * kSize);
   size_t start = heap->NewSpaceAllocationCounter();
   for (int i = 0; i < 20; i++) {
     AllocateInSpace(isolate, kSize, NEW_SPACE);
     size_t counter = heap->NewSpaceAllocationCounter();
     CHECK_EQ(kSize, counter - start);
     start = counter;
   }
@@ skipping 153 matching lines @@
   size_t counter2 = 2000;
   tracer->SampleAllocation(time2, counter2, counter2);
   size_t throughput = tracer->AllocationThroughputInBytesPerMillisecond(100);
   CHECK_EQ(2 * (counter2 - counter1) / (time2 - time1), throughput);
   int time3 = 1000;
   size_t counter3 = 30000;
   tracer->SampleAllocation(time3, counter3, counter3);
   throughput = tracer->AllocationThroughputInBytesPerMillisecond(100);
   CHECK_EQ(2 * (counter3 - counter1) / (time3 - time1), throughput);
 }