Reduce signal sender thread stack size to 32k.

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
===================================================================
--- test/cctest/test-heap.cc	(revision 10368)
+++ test/cctest/test-heap.cc	(working copy)
@@ -1198,17 +1198,14 @@
        obj = iterator.next()) {
     size_of_objects_2 += obj->Size();
   }
-  // Delta must be within 5% of the larger result.
-  // TODO(gc): Tighten this up by distinguishing between byte
-  // arrays that are real and those that merely mark free space
-  // on the heap.
+  // Delta must be within 1% of the larger result.
   if (size_of_objects_1 > size_of_objects_2) {
     intptr_t delta = size_of_objects_1 - size_of_objects_2;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "
            "Iterator: %" V8_PTR_PREFIX "d, "
            "delta: %" V8_PTR_PREFIX "d\n",
            size_of_objects_1, size_of_objects_2, delta);
-    CHECK_GT(size_of_objects_1 / 20, delta);
+    CHECK_GT(size_of_objects_1 / 100, delta);
   } else {
     intptr_t delta = size_of_objects_2 - size_of_objects_1;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "