Fix identifier size in the heap dump.
Fix identifier size in the heap dump.

We're using addresses as IDs and previously we would have written
sizeof(void*) as the identifier size in the header. Heap references
are actually uint32_t so writting 4 bytes should be enough.

Bug: 16016862
Change-Id: I785abf5030681b6009370b7b2d7552e8b4b54e67

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst