### Description
This PR updates the version of Dawn to
`b9b4a37041dec3dd62ac92014a6cc1aece48d9f3` (ref:
[chromium](67f86f01dd/DEPS (399)))
in the `deps.txt` file.
The newer version of Dawn includes the previous changes from dawn.patch
so that we can remove the patch file.
There is a little interface changes and code is updated correspondingly.
