Add cull rect visualization to debugger

This adds cull rect visualization to the debugger's "mega" visualization mode.

Committed: http://code.google.com/p/skia/source/detail?r=13649

[f(malita), 2014-03-03 22:21:18]

LGTM.

If I grok this, it will show active cull rects for a given command index. That's
useful, but eventually I would like to also add a heatmap-style cull rect
visualization mode (showing *all* cull rects in a given SKP, overlaid somehow -
semi-transparent?). That would provide a quick global view of how content is
grouped for culling purposes.

[robertphillips, 2014-03-03 22:30:01]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-03-03 22:30:02]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-03 22:30:02]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[fmalita_google_do_not_use, 2014-03-03 22:30:39]

On 2014/03/03 22:30:02, I haz the power (commit-bot) wrote:
> No LGTM from a valid reviewer yet. Only full committers are accepted.
> Even if an LGTM may have been provided, it was from a non-committer or
> a lowly provisional committer, _not_ a full super star committer.
> See http://www.chromium.org/getting-involved/become-a-committer
> Note that this has nothing to do with OWNERS files.

LGTM.

[fmalita_google_do_not_use, 2014-03-03 22:30:51]

The CQ bit was checked by fmalita@google.com

[commit-bot: I haz the power, 2014-03-03 22:30:52]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/robertphillips@google.com/177423013/1

[robertphillips, 2014-03-03 22:34:40]

That mode would be pretty easy to add - it would just entail making all the
culls up to the current render index active (instead of pushing and popping
them). For UI we could add an 'all' vs. 'current' button to the debugger. To
honor this for the clips we would have to extend the "active" system to them and
then disable the SkCanvas clip stack playback system in 'all' mode.

[commit-bot: I haz the power, 2014-03-03 23:25:43]

Change committed as 13649