Async Clipboard: Specify exceptions

- Previously, async clipboard promise rejections had no DOMException tied to
them. This CL adds exceptions for when async clipboard operations fail.
- These are simply mock exceptions until more precise exceptions are added into
the spec.

Bug: 150835
Change-Id: I3f4352352f48274ca659672d455d92801d89919e
Reviewed-on: https://chromium-review.googlesource.com/c/1464077
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631416}
3 files changed