Add SkOverdrawCanvas to detect overdraw

Add SkOverdrawCanvas to detect overdraw

This is the first part of a multi-part change to detect and
display gpu overdraw on Android.

BUG:32370375

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4907

Change-Id: Ibba9d7343f2fd57397fa1168a5a5b1ef6ef91287
Reviewed-on: https://skia-review.googlesource.com/4907
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>