[jumbo] Give two GetPromoStringSpecifier() functions unique names

In jumbo builds many cc files compile together in the same
translation unit and then they share the same anonymous namespace.
That means that within a (jumbo) build target, also symbols in
anonymous namespaces need (build target) unique names.

In a recent patch, two GetPromoStringSpecifier functions appeared.
They are almost identical but not quite, so this patch just
gives them unique names to make all jumbo build configurations
happy again. Most jumbo build configurations were already happy
because the relevant files did not easily end up in the same
jumbo chunk.

See https://chromium-review.googlesource.com/c/1298394

TBR=collinbaker@chromium.org,bsep@chromium.org,nyquist@chromium.org,robliao@chromium.org

Change-Id: I5f244fc6a4e5b2047f2fdb443d0e40565c8bc103
Reviewed-on: https://chromium-review.googlesource.com/c/1309739
Reviewed-by: Daniel Bratell <bratell@opera.com>
Reviewed-by: Robert Liao <robliao@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604284}
2 files changed