Don't assert if glCheckFramebufferStatus fails

This can fail if the context has been reset or abandoned. Instead return
false so the caller print a warning message and skip rendering.

Bug: chromium:1235232
Bug: skia:12258
Bug: skia:5200
Change-Id: If78a914a25d09d48477e04317a34473632f76207
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/435816
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1 file changed