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* With this turned on, gtest unconditionally asks absl to initialize
  the symbol handler.  This causes base's attempt to do the same thing
  to fail.  Make base handle this by trying a force-reinit if this
  failure occurs.
* Allow gtest to see the full absl sources, since it unconditionally
  #includes banned headers.
* Fix include dirs not being set correctly, leading to compile failures.
* Narrow gtest absl dependency from public_deps to deps, since we don't
  want "all targets depending on gtest" to silently be able to use absl.
* Leave this flag disabled by default for NaCl, since the toolchain
  there can't compile some of the absl code.

Bug: none
Change-Id: I24930d1c2086bec1522922665708abee5ce8fc08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332038
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#793786}