Serialize heap snapshot data as an array of unsigned values.

Serialize heap snapshot data as an array of unsigned values.

None of the values can in fact be negative, while object IDs
can have the highest bit set which lead to negative values appear
in the snapshot that front-end is unable to parse.

Committed: https://code.google.com/p/v8/source/detail?r=11553

[yurys, 2012-05-12 16:26:33]

lgtm

http://codereview.chromium.org/10356143/diff/1/src/profile-generator.cc
File src/profile-generator.cc (right):

http://codereview.chromium.org/10356143/diff/1/src/profile-generator.cc#newco...
src/profile-generator.cc:3502: static int utoa(unsigned value, const
Vector<char>& buffer, int buffer_pos) {
Not directly related to this change but we need to do something about
v8::RetainedObjectInfo::GetHash return value to make sure the ids are unique
after hashing.