This updates the gdb bitmap viewer for color enums, SkBitmap layout, and
to work with gdb when using python 2.
Change-Id: Id50048ecd7db5b3febaff15f118d8b8183c7dbf1
Reviewed-on: https://skia-review.googlesource.com/136247
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>