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Startup tracing is broken for several reasons:

1. When renderers are forked from a Zygote process, --trace-startup
   flags are ignored.

2. In a non-zygote mode, when --trace-config-file is used, it is
   ignored since sandboxed renderers do not have access to file
   system.

3. Another bug is that --trace-config-file is always passed to
   renderer processes, even if they are created after tracing is
   stopped, e.g. via DevTools.

4. Startup tracing flags are not passed along to the ppapi plugin
   and utility processes.

This CL fixes 1, 3, and 4 and partially fixes 2 by passing categories
and record mode of a trace config file using flags to sandboxed
renderer processes so that they do not need to ready these information
from a file. Obviously, this does not work for complex trace config
files, but should be enough to resolve existing telemetry issues
(please see discussions in crbug.com/809833).

Bug: 809833
Change-Id: I6723664fd477117262763476c0a86fd6881b94a7
Reviewed-on: https://chromium-review.googlesource.com/972145Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545950}