Mac -fno-threadsafe-statics

Use -fno-threadsafe-statics to disable thread-safe static semantics in C++.
This will eliminate the cxa_guard_acquire/release locks around static guard
accesses.  The Windows compiler doesn't support thread-safe statics at all,
so none of our cross-platform code relies on thread safety.  We are using
-fno-threadsafe-statics on Linux as well, since r20616.  It's likely that
threading is not a concern in most to all Mac-specific code using statics.

BUG=16713
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=23326

[Mark Mentovai, 2009-08-13 16:20:45]

Unless someone volunteers to audit the use of statics in Mac-specific code, I
think we should just try this and see if it breaks anything.  I suspect that
most of our Mac-specific code isn't expecting to be threaded anyway.

[Mark Mentovai, 2009-08-13 17:57:35]

TVL is mostly unreachable today, let's try Stuart.

[stuartmorgan, 2009-08-13 18:03:14]

LGTM