This is a mechanical conversion from the original HTML page to markdown
doc with few typo fixes, link fix and reformatting.

See http://go/clank/engineering/android-webview/java-bridge for the
original doc.

Fix: 948816
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: I503c964bc6445ce26b8d9aea3cfd03bf77667c73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391771
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804382}