Fix double-accounting of SkPictureShader bitmap memory

The pixels RAM is accounted via SkImageGenerator/SkImageCacherator, we
don't need to report it as part of SkPictureShader's BitmapShaderRec.

R=reed@google.com
BUG=chromium:619929
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2415673002

Review-Url: https://codereview.chromium.org/2415673002
1 file changed