Fix recursive computation of filter bounds for drop shadow,

Fix recursive computation of filter bounds for drop shadow,
morphology, blur.

[Reland with fixed tests.]

Because we're computing "backwards" from a clip rect of destination
pixels to be filled to the required source pixels, we should use tail
recursion rather than head recursion in onFilterBounds().

This actually only makes a difference for drop-shadow, where
the computation is non-commutative. Blur and morphology commute, but I
moved them to tail recursion anyway for clarity (so all onFilterBounds
use tail recursion).

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/1150a6d151571fb6ee816dadec844ae7ab53948a

[Stephen White, 2014-08-22 21:59:40]

Brian: PTAL. Thanks!

[bsalomon, 2014-08-25 14:22:55]

lgtm

[Stephen White, 2014-08-25 14:59:28]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-08-25 15:00:02]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/senorblanco@chromium.org/481273005/1

[commit-bot: I haz the power, 2014-08-25 15:07:03]

Committed patchset #1 (1) as 28648fe4a69b0cee8df42b5966e4e645c3aabefb

[djsollen, 2014-08-25 16:05:29]

A revert of this CL (patchset #1) has been created in
https://codereview.chromium.org/504773003/ by djsollen@google.com.

The reason for reverting is: This CL is currently breaking the Win7 and Win8
bots on some of the new tests (in DM)..

[Stephen White, 2014-08-25 19:38:07]

Relanding with test fixed.

[Stephen White, 2014-08-25 19:38:42]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2014-08-25 19:39:19]

CQ is trying da patch. Follow status at

https://skia-tree-status.appspot.com/cq/senorblanco@chromium.org/481273005/20001

[commit-bot: I haz the power, 2014-08-25 19:47:04]

Committed patchset #2 (20001) as 1150a6d151571fb6ee816dadec844ae7ab53948a