Revert of third try at landing improved blur rect; this time with more correctness

Revert of third try at landing improved blur rect; this time with more correctness (https://codereview.chromium.org/331443003/)

Reason for revert:
Failing layout test: https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux/32762/layout-test-results/virtual/gpu/fast/canvas/canvas-draw-canvas-on-canvas-shadow-pretty-diff.html

Original issue's description:
> third try at landing improved blur rect; this time with more correctness
> 
> BUG=skia:2095
> R=bsalomon@google.com
> TBR=bsalomon
> 
> Committed: https://skia.googlesource.com/skia/+/72abfc2b4e7caead660f6b6a05e60d05eaf1a66f

TBR=bsalomon@google.com,reed@google.com,humper@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2095
Committed: https://skia.googlesource.com/skia/+/e07c1ab40882078b505f2b0ceb7413c44af569e8

[scroggo, 2014-06-12 19:10:04]

Created Revert of third try at landing improved blur rect; this time with more
correctness

[commit-bot: I haz the power, 2014-06-12 19:10:17]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/scroggo@google.com/333763002/1

[commit-bot: I haz the power, 2014-06-12 19:10:29]

Change committed as e07c1ab40882078b505f2b0ceb7413c44af569e8