Replace uint64_t type with ObjectId and use uint32_t as the base for ObjectId type.

We have a problem with really big apps. The snapshot for such pages doesn't fit into JS heap on DevTools front-end side. I'd like to move the snapshot's nodes data into Int32Array.
This will reduce the pressure. At this moment it is not possible because the snapshot uses uint64_t for ids. 

BUG=none
TEST=profiler-generator tests

[mnaganov (inactive), 2012-03-06 14:56:03]

On 2012/03/06 14:36:13, loislo wrote:

It's an interesting idea. But I have a concern about v8::RetainedObjectInfo
instances which are currently just returning their pointer as a hash value (see
in V8GCController.cpp): 

virtual intptr_t GetHash()
{
    return reinterpret_cast<intptr_t>(m_object);
}

Perhaps we first need to address this issue by changing GetHash to return a real
uint32_t hash value. WDYT?

[alexeif, 2012-03-06 16:07:52]

https://chromiumcodereview.appspot.com/9617006/diff/1/src/profile-generator.cc
File src/profile-generator.cc (right):

https://chromiumcodereview.appspot.com/9617006/diff/1/src/profile-generator.c...
src/profile-generator.cc:3538: STATIC_CHECK(sizeof(uint32_t) ==
sizeof(entry->id()));  // NOLINT
It should be 'unsigned'. The idea here is to check the types against the printf
format codes used below. The 'id' is printed with %u.

Otherwise once we hit an arch having 64-bit int type the check won't trigger and
we silently pass 32-bit value into printf which would expect 64-bit value.

[mnaganov (inactive), 2012-03-08 15:31:22]

LGTM with comments

https://chromiumcodereview.appspot.com/9617006/diff/2001/src/profile-generato...
File src/profile-generator.cc (right):

https://chromiumcodereview.appspot.com/9617006/diff/2001/src/profile-generato...
src/profile-generator.cc:1475: Handle<HeapObject>
HeapSnapshotsCollection::FindHeapObjectById(SnapshotObjectId id) {
nit: 80 chars

https://chromiumcodereview.appspot.com/9617006/diff/2001/src/profile-generato...
src/profile-generator.cc:3532: + MaxDecimalDigitsIn<sizeof(uint32_t)>::kUnsigned
 // NOLINT
Perhaps, using SnapshotObjectId here will make it clear, why we want to always
use 32-bit type?