Call notifyPixelsChanged after modifying bitmap

Call notifyPixelsChanged after modifying bitmap

In CodecSrc's scanline_subset test, we decode a subset of an image to a
bitmap, draw it to the canvas, and then repeat. This is fine for most
backends, but not for pipe. Pipe sees the same generation ID, so it
assumes it is the same bitmap it saw before, and just draws the
original one.

Call notifyPixelsChanged, so the bitmap will get a new generation ID,
fixing pipe.

BUG=skia:4138
Committed: https://skia.googlesource.com/skia/+/4358f13ac614d572c137e95748c6dc2ca0d66784

[scroggo_chromium, 2015-07-30 17:58:19]

scroggo@chromium.org changed reviewers:
+ emmaleer@google.com, msarett@google.com

[scroggo_chromium, 2015-07-30 17:58:19]

We may still want to veto pipe from CodecSrcs, but this fixes the bug.

[msarett, 2015-07-30 18:20:41]

lgtm

I think this bug is a good reason to make sure that we continue to test on
pipe-8888.

This also make me think that it's a good thing that we want to add dm tests for
classes that use SkCodec (ex:BitmapRegionDecoder) because I can very easily see
myself forgetting to make this call.

[scroggo, 2015-07-30 18:23:39]

The CQ bit was checked by scroggo@google.com

[commit-bot: I haz the power, 2015-07-30 18:23:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1265983004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1265983004/1

[commit-bot: I haz the power, 2015-07-30 18:33:07]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/4358f13ac614d572c137e95748c6dc2ca0d66784