We can use the one from //lib/tonic instead.

This removes most (all?) of our dependency on base::RefCountedThreadSafe.

Also pick up some needed fixes to FTL and Tonic

* Roll Dart to pickup new BoringSSL

* Roll further to pick up build file fixes

WTF is now //base clean.

We don't have a way to print stack traces on Fuchsia yet. This patch
isolates this base dependency in //glue.

Previously we had created a resource context for each PlatformView which would
be destroyed when the PlatformView lost its surface.

Fixes https://github.com/flutter/flutter/issues/5200

The ftl::TaskRunner is still based on a base::MessageLoop, but this patch paves
the way to replace the message loop on Fuchsia.

Fixes https://github.com/flutter/flutter/issues/4957

PlatformViews are owned by the UI thread

Add collection of PlatformViews to the Shell and allow them to be queried over the service protocol (#2861)

* Adopt //lib/tonic/logging

* Adopt //lib/tonic/scopes

* Adopt //lib/tonic/parsers

Also, switch over to //lib/tonic's typed data classes.

Hopefully this will build this time.

* Remove time

* Remove rand

* Remove array buffers

* Remove more code

* Remove more image decoding code

* Remove more code

* Remove old public API

* Remove more old public headers

* Remove layout test support

* Remove WebPrivateOwnPtr

* Remove WebString

* Remove worker pool

We will eventually remove our version of tonic and use this one instead.

This patch removes a bunch of dead code in //skia/ext.

Also, remove the hacks that integrate Skia ref counting with WTF. Now we
just use sk_sp everywhere for managing Skia ref counts.