Chrome custom tabs are not webview.

What should the detached request support in the benchmark do?

Are we going to (1) compare time to "first contentful paint" with/without the detached request or (2) test detached request multiple times in a row and search for outliers?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f76200ab96bb9ddfd91f9b31499fb73eeb41c692

commit f76200ab96bb9ddfd91f9b31499fb73eeb41c692
Author: Jean-denis Muys <jdmuys@chromium.org>
Date: Wed Oct 10 14:23:31 2018

added support for CCTParallelRequest to CustomTabsBenchmark

This test application is used with customtabs_benchmark.py script to
test CCT automatically. It can now also test the detached request
feature that allow CCT to load the first URL of a redirect chain in
parallel to the last.

Bug: 891312
Change-Id: I223b7206ab6953e4c307c91ab5cd0ba3a52825c5
Reviewed-on: https://chromium-review.googlesource.com/c/1238895
Reviewed-by: Benoit L <lizeb@chromium.org>
Commit-Queue: Jean-Denis Muys <jdmuys@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598311}
[modify] https://crrev.com/f76200ab96bb9ddfd91f9b31499fb73eeb41c692/tools/android/customtabs_benchmark/java/src/org/chromium/customtabs/test/MainActivity.java
[modify] https://crrev.com/f76200ab96bb9ddfd91f9b31499fb73eeb41c692/tools/android/customtabs_benchmark/res/layout/main.xml
[modify] https://crrev.com/f76200ab96bb9ddfd91f9b31499fb73eeb41c692/tools/android/customtabs_benchmark/res/values/strings.xml
[modify] https://crrev.com/f76200ab96bb9ddfd91f9b31499fb73eeb41c692/tools/android/customtabs_benchmark/scripts/customtabs_benchmark.py