Adding a PictureResolution option to SkPictureImageFilter

This change adds an option to SkPictureImageFilter to make it
rasterize SkPicture in a resolution that matches the local coordinate
space (equivalent to the record-time device space).

BUG=skia:3176
R=reed@google.com, senorblanco@chromium.org

Review URL: https://codereview.chromium.org/753073010
rebaseline after clear change -- pdf was not treating clear as SRC_MODE

BUG=skia:
NOTRY=True
TBR=

Review URL: https://codereview.chromium.org/759303004
Remove SK_SUPPORT_DEPRECATED_SCALARROUND.

Our clients no longer require it.

Review URL: https://codereview.chromium.org/772933002
baseline colorwheelnative

TBR=scroggo@google.com
NOTRY=true

Review URL: https://codereview.chromium.org/777443002
implement device::clear until we can remove callers in chrome skia/ext

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/773903002
Flail a little against LLVM crash.

Cannot reproduce this in my local Chromium checkout (using their Clang, just like the bots).

BUG=skia:

TBR=reed@google.com

Review URL: https://codereview.chromium.org/764433003