GitLab

When a share target has method GET, we set the url's query using
application/x-www-form-urlencoded serialization results.

Spec:
https://w3c.github.io/web-share-target/level-2/#launching-the-web-share-target

Design doc:
https://docs.google.com/document/d/1E4CYASFDVNqmyCbaxa8u8sOn0-Sc1miLeZfA3t3ou5o/edit#

Bug: 1125880
Change-Id: I09dc04df1535eb6e8cb0fc1fa61d926c7808ffef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2590927Reviewed-by: Alan Cutter <alancutter@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836912}