SkPDFImage no longer caches a unpremul version of N32 bitmaps.

SkPDFImage no longer caches a unpremul version of N32 bitmaps.

This reduces PDF memory overhead by 30% over all GMs.

This reduces PDF memory overhead by 41% over all SKPs in
chromium-skia-gm/playback_${SKP_VERSION}/skps.

BUG=skia:3030
Committed: https://skia.googlesource.com/skia/+/549f879d6a8c420fb510491fe49f2618bb0ba2c3

[hal.canary, 2015-01-06 22:36:18]

halcanary@google.com changed reviewers:
+ djsollen@google.com, reed@google.com

[hal.canary, 2015-01-06 22:36:19]

ptal

[hal.canary, 2015-01-06 22:37:55]

The CQ bit was checked by halcanary@google.com

[commit-bot: I haz the power, 2015-01-06 22:38:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/840653002/1

[commit-bot: I haz the power, 2015-01-06 22:38:32]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-01-07 04:38 UTC

[hal.canary, 2015-01-06 22:38:51]

The CQ bit was unchecked by halcanary@google.com

[hal.canary, 2015-01-08 18:18:52]

PTAL at the simplified CL

[reed1, 2015-01-08 18:29:48]

lgtm w/ request for comment

https://codereview.chromium.org/840653002/diff/20001/src/pdf/SkPDFImage.cpp
File src/pdf/SkPDFImage.cpp (right):

https://codereview.chromium.org/840653002/diff/20001/src/pdf/SkPDFImage.cpp#n...
src/pdf/SkPDFImage.cpp:163: c = get_argb8888_neighbor_avg_color(bitmap, x, y);
// we average the neighbors so that ... (?)

[hal.canary, 2015-01-08 18:56:21]

The CQ bit was checked by halcanary@google.com

[commit-bot: I haz the power, 2015-01-08 18:57:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/840653002/40001

[commit-bot: I haz the power, 2015-01-08 19:05:39]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/549f879d6a8c420fb510491fe49f2618bb0ba2c3