Reduce boot-up memory use of V8.

Reduce boot-up memory use of V8.
This is a recommit of http://codereview.chromium.org/9179012
after fixing what turned out to be unrelated out-of-memory
errors.
That was a rebase of http://codereview.chromium.org/9017009/
Committed: https://code.google.com/p/v8/source/detail?r=10542

[Vyacheslav Egorov (Chromium), 2012-01-26 16:12:00]

LGTM with comments addressed.

https://chromiumcodereview.appspot.com/9289047/diff/1/src/heap.cc
File src/heap.cc (right):

https://chromiumcodereview.appspot.com/9289047/diff/1/src/heap.cc#newcode588
src/heap.cc:588: while (gc_performed) {
it seems to me that this loop can go on forever. can you prove that we are not
going to loop here forever doing GC if OS refuses us new pages and we at the
boundary of soft/hard limit?

https://chromiumcodereview.appspot.com/9289047/diff/1/src/spaces.h
File src/spaces.h (right):

https://chromiumcodereview.appspot.com/9289047/diff/1/src/spaces.h#newcode1598
src/spaces.h:1598: void IncreaseUnsweptFreeBytes(Page* p) {
I wonder if this needs to be adjusted somehow to accomodate pages that are
smaller than kObjectAreaSize.

(this is used to provide estimate of SizeOfObjects when lazy sweeping is active.
can lazyly swept pages be partially uncommitted?)