Add source-side perf upload script for WebRTC.

This effectively makes WebRTC upload histogram sets instead of Chart
JSON. Histogram sets is the newest format used by Chromium. I'm doing
this because it's nice to use the most modern thing, but mostly because
it's the default for PinPoint. This means I don't have to implement and
support a new read quest for Chart JSON.

This script has to be source side, because we need third_party/catapult
to write correct histograms. This script will be called from recipes.

I also considered generating histogram JSON directly in
test/testsupport/perf_test.cc, which could have avoided this conversion
from Chart JSON to histogram sets, but I can't because there is no C++
API for histogram sets.

Bug: webrtc:11084
Change-Id: If0d2315d2057112b3c2d54a9cfd12e59b5858a18
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159780
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29818}

.vpython

@@ -31,6 +31,12 @@ wheel: <
   version: "version:5.2.2"
 >
 
+# Used by tools_webrtc/perf/webrtc_dashboard_upload.py.
+wheel: <
+  name: "infra/python/wheels/httplib2-py2_py3"
+  version: "version:0.10.3"
+>
+
 # Used by:
 #   build/toolchain/win
 wheel: <