Band-aid for subsetted bitmaps in SKPs.

Band-aid for subsetted bitmaps in SKPs.

Partial fix for https://code.google.com/p/skia/issues/detail?id=1301.

Instead of firing an assert when the recorded width and height do
not match the encoded data's width and height, take a subset of
the bitmap of the correct size.

The bitmap may be drawn incorrectly, since it will not necessarily
be the correct subset (though it will be the correct size). The
complete fix will be to record the offset to the stream. Holding off
on that since it will change the PICTURE_VERSION. There is still 
more work to do on read/writeBitmap, and I would like to change
PICTURE_VERSION as few times as possible.

BUG=https://code.google.com/p/skia/issues/detail?id=1301
R=djsollen@google.com

Committed: https://code.google.com/p/skia/source/detail?r=9169

[djsollen, 2013-05-16 19:35:06]

lgtm

[scroggo, 2013-05-16 19:35:45]

Committed patchset #2 manually as r9169 (presubmit successful).