IndexedDB: Fix WPT bindings-inject-key to clean up Object.prototype

Add a new cleanup for the 'prototype chain' test to fix a crash that
happens when the test is run under chromedriver.  Update the other
tests to use t.add_cleanup() so they follow our test best practices.

The underlying chromedriver issue is tracked upstream at
https://crbug.com/chromedriver/2555.

Bug: 934844
Change-Id: Id1b4ab2a908bfbc001e2a2d045eeec3ef01c24d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497613
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637410}
1 file changed