switching to catapult/tracing

but found that appengine/third_party/catapult is too old?
It hits 'Object.observe is not function' error, like  http://crbug.com/569417 
https://github.com/catapult-project/catapult/issues/1848

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra.git/+/ff3c8af68a63bce6eb220f49472997d3162992a6

commit ff3c8af68a63bce6eb220f49472997d3162992a6
Author: ukai <ukai@chromium.org>
Date: Wed Apr 27 04:08:37 2016

chromium_build_stats: fix trace viewer

generate trace-viewer.html by go generate

trace-viewer.html uses <script id="viewer-data" type="text/plain"> for
embedded data, instead of "application/json".

depends on catapult roll: https://codereview.chromium.org/1921913005/
to generate correct trace-viewer.html

BUG= 519334 , 606663 

Review URL: https://codereview.chromium.org/1916363002

[modify] https://crrev.com/ff3c8af68a63bce6eb220f49472997d3162992a6/appengine/chromium_build_stats/README.md
[modify] https://crrev.com/ff3c8af68a63bce6eb220f49472997d3162992a6/appengine/chromium_build_stats/default/ninja_log.go
[delete] https://crrev.com/c5e1098d5aab949364ea5d58f8d4a95676d56101/appengine/chromium_build_stats/gen-trace-viewer.sh
[modify] https://crrev.com/ff3c8af68a63bce6eb220f49472997d3162992a6/appengine/chromium_build_stats/gopath/src/ninjalog/traceviewer/traceviewer.go