Refactoring only: Extracted 2 methods from ClearNonLiveTransitions

Refactoring only: Extracted 2 methods from ClearNonLiveTransitions

This simple refactoring makes it very clear that clearing non-live transitions
actually consists of 2 quite separate things. Things would even be nicer if the
prototype transitions were represented by a separate data structure instead of
reusing FixedArray in an interesting way once again.

As an additional bonus, this CL makes it possible to read each of the methods in
question on a 30" screen without scrolling!

Committed: https://code.google.com/p/v8/source/detail?r=10501

[Michael Starzinger, 2012-01-25 13:15:47]

LGTM (if comments are addressed).

https://chromiumcodereview.appspot.com/9169045/diff/1/src/mark-compact.cc
File src/mark-compact.cc (right):

https://chromiumcodereview.appspot.com/9169045/diff/1/src/mark-compact.cc#new...
src/mark-compact.cc:2367: void
MarkCompactCollector::ClearNonLiveMapTransitions(Map* map, bool marked) {
I don't like boolean flags, they are very confusing. Can we instead pass the
map's MarkBit (i.e. map_mark)? Thereby you can reuse that as the initial
current_mark value as well and it is clear what that argument means.

https://chromiumcodereview.appspot.com/9169045/diff/1/src/mark-compact.cc#new...
src/mark-compact.cc:2382: MarkBit current_mark = Marking::MarkBitFrom(current);
Like the above comment said: Initialize outside of loop and update at end of
loop after line 2398.