[Browser/WebTaskEnvironment] Mass-migrate away from Test(Browser|Web)ThreadBundle

This is
 1) s/TestBrowserThreadBundle/BrowserTaskEnvironment/ on src/
 2) s/([^/])\b\w*thread_bundle(_)?/\1task_environment\2/ on files modified in (1)
 3) git cl format
 4) Manually fix up remainder "ThreadBundle" and "thread_bundle" found via
    string search on the whole of src/.

For ease of review:
 * Step #3 is the diff between patch sets 1..2
 * Step #4 is the diff between patch sets 2..3

[email protected]
(for post-review owners bypass per mechanical change)

Bug: 992483
Change-Id: I4945141f6d78bdc6c98444198e5012ddc8e5bff0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1758440
Reviewed-by: Gabriel Charette <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Commit-Queue: Gabriel Charette <[email protected]>
Auto-Submit: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#688755}
diff --git a/docs/threading_and_tasks.md b/docs/threading_and_tasks.md
index c48b624..13caf78 100644
--- a/docs/threading_and_tasks.md
+++ b/docs/threading_and_tasks.md
@@ -631,7 +631,7 @@
 instantiate a
 [`base::test::TaskEnvironment`](https://cs.chromium.org/chromium/src/base/test/scoped_task_environment.h)
 for the scope of the test. If you need BrowserThreads, use
-`content::TestBrowserThreadBundle` instead of
+`content::BrowserTaskEnvironment` instead of
 `base::test::TaskEnvironment`.
 
 Tests can run the `base::test::TaskEnvironment`'s message pump using a