Update IPC ParamTraits for SkBitmap to follow best practices.

Using memcpy() to serialize a POD struct is highly discouraged. Just use
the standard IPC param traits macros for doing it.

Bug: 779428
Change-Id: I48f52c1f5c245ba274d595829ed92e8b3cb41334
Reviewed-on: https://chromium-review.googlesource.com/899649
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534562}