Improve dial_internal_message_fuzzer

- Limit input size to prevent out-of-memory failures
- Test DialInternalMessageUtil::IsStopSessionMessage()

Also make DialInternalMessageUtil::IsStopSessionMessage() static,
because it doesn't need to be an object method

Bug: 960013
Change-Id: Ic5edb1d326dac7ce98b9e50dbf6497593444ed60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1622426
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661909}
5 files changed