Revert "Share DWriteFontProxyImpl TaskRunner to DWriteFontLookupTableBuilder"

This reverts commit 0e244ee9ed5d95d8114fd49292e799f1d7f507d4.

Reason for revert: Causes flakiness in FontUniqueNameBrowserTest.ContentLocalFontsMatching

Original change's description:
> Share DWriteFontProxyImpl TaskRunner to DWriteFontLookupTableBuilder
> 
> Preparation for a follow-up CL that actually making queries for the font
> lookup table asynchronous. In that CL, DWriteFontLookupTableBuilder
> needs the task runner to run the Mojo message callback on the same task
> runner on which DWriteFontProxyImpl received it.
> 
> Move scheduling the lookup table construction to
> common_browser_interfaces.cc which is still around the same time in
> startup as before, but makes it much easier to share the same task
> runner.
> 
> Bug: 960263, 889864
> Tbr: avi
> Change-Id: I8be6d4a4d29014967d38f20ccf8a94948a7b8a1e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626865
> Commit-Queue: Dominik Röttsches <drott@chromium.org>
> Reviewed-by: Dominik Röttsches <drott@chromium.org>
> Reviewed-by: Ken Rockot <rockot@google.com>
> Reviewed-by: François Doray <fdoray@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#663021}

TBR=avi@chromium.org,rockot@google.com,fdoray@chromium.org,drott@chromium.org

Change-Id: Ie88de224e40862a3fa62618c553501e51aa29599
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 960263, 889864
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628712
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663039}
3 files changed