Refactor PictureRecord optimization & added saveLayer/save/clipR/DBM*/restore/restore optimization

This CL moves the second optimization over from the filter tool into PictureRecord. This new optimization looks for the pattern:
SAVE_LAYER
   SAVE
      CLIP_RECT
      DRAW_BITMAP*
   RESTORE
RESTORE
where the saveLayer's paint can be folded into the drawBimap*'s.

Additionally some minor refactoring of the optimizations has been performed including:
 splitting off a merge_savelayer_paint_into_drawbitmp subroutine
 adding a convert_command_to_noop method
 adding an array of optimization function pointers
 adding a generic matching method ('match')

Performance numbers are in-line with what was seen in https://codereview.appspot.com/7294049/

[robertphillips, 2013-03-07 18:07:54]

Comments on this?

[robertphillips, 2013-03-11 16:23:32]

ping

[reed1, 2013-03-11 16:37:07]

lgtm -- unless...

does it make sense to separate out the input (request-op/*) and output
(op+offset+len)? If so, it simplifies a bit the (nice) data-driven setup for a
given optimization:

input = { DRAW_SAVELAYER, DRAW_SAVE, DRAW_BITMPA, RESTORE, RESTORE };
output[5];

...

[robertphillips, 2013-03-12 15:40:03]

Done.

committed as r8106