SkClipStack::Element tweaks.

SkClipStack::Element tweaks.

(
This is intended to facilitate efficient kMatrix_SaveFlags emulation
on restore():

  * collect all clip stack elements for the current save count into a
    side clip stack
  * canvas.restore(everything)
  * replay the collected clip ops to restore the initial clip state
  => we restored the matrix but the clip state is unchanged
)

Two main changes:

  * expose the save count for SkClipStack::Element
  * expose a replay method for the same (logic relocated from
    SkCanvas::replayClips)

The SkCanvas::ClipVisitor shuffling is to enable forward decl
in SkClipStack.h (cannot fwdecl a nested class).

R=robertphillips@google.com
TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/c3b589a24eb4d567a906189f882c259ecf5c2f58

[f(malita), 2014-05-02 01:52:50]

This is a WIP as the Android change is not ironed out yet. I'm guessing we'll
have to expose the save count, but the other changes may be optional.

[robertphillips, 2014-05-02 12:35:38]

lgtm

https://codereview.chromium.org/269693003/diff/1/include/core/SkCanvas.h
File include/core/SkCanvas.h (right):

https://codereview.chromium.org/269693003/diff/1/include/core/SkCanvas.h#newc...
include/core/SkCanvas.h:1500: 
I know this isn't due to this CL but, why isn't clipRegion in here?

[f(malita), 2014-05-02 12:59:26]

https://codereview.chromium.org/269693003/diff/1/include/core/SkCanvas.h
File include/core/SkCanvas.h (right):

https://codereview.chromium.org/269693003/diff/1/include/core/SkCanvas.h#newc...
include/core/SkCanvas.h:1500: 
On 2014/05/02 12:35:38, robertphillips wrote:
> I know this isn't due to this CL but, why isn't clipRegion in here?

You just put your finger on my biggest concern: SkClipStack doesn't store
SkRegion info at all! SkCanvas::clipRegion() devolves into a clipRect():

    // todo: signal fClipStack that we have a region, and therefore (I guess)
    // we have to ignore it, and use the region directly?
    fClipStack.clipDevRect(rgn.getBounds(), op);

I guess this means using the clip stack for replay will break clipRegion users?

[f(malita), 2014-06-04 23:25:52]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2014-06-04 23:26:36]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/fmalita@chromium.org/269693003/20001

[commit-bot: I haz the power, 2014-06-04 23:26:39]

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

[commit-bot: I haz the power, 2014-06-04 23:26:39]

Presubmit check for 269693003-20001 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com')

[f(malita), 2014-06-05 19:09:12]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2014-06-05 19:09:35]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/fmalita@chromium.org/269693003/20001

[commit-bot: I haz the power, 2014-06-05 19:09:43]

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

[commit-bot: I haz the power, 2014-06-05 19:09:46]

Presubmit check for 269693003-20001 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com')

[reed1, 2014-06-05 19:16:23]

lgtm

[f(malita), 2014-06-05 19:18:33]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2014-06-05 19:19:20]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/fmalita@chromium.org/269693003/20001

[commit-bot: I haz the power, 2014-06-05 19:40:16]

Change committed as c3b589a24eb4d567a906189f882c259ecf5c2f58