Linux: don't use GOT patching to intercept localtime(_r)

Linux: don't use GOT patching to intercept localtime(_r)

Our current GOT patching code is platform specific and fails to work
when V8 is built as a library.

Instead we define global functions for those functions which we wish
to override.  Since we will be first in the dynamic resolution order,
the dynamic linker will point callers to our versions of these
functions. However, we have the same binary for both the browser and
the renderers, which means that our overrides will apply in the
browser too.

The global |global_am_zygote_or_renderer| is true iff we are in a
zygote or renderer process. It's set in ZygoteMain and inherited by
the renderers when they fork. (This means that it'll be incorrect for
global constructor functions and before ZygoteMain is called -
beware).

Our replacement functions can check this global and either proxy the
call to the browser over the sandbox IPC
(http://code.google.com/p/chromium/wiki/LinuxSandboxIPC) or they can
use dlsym with RTLD_NEXT to resolve the symbol, ignoring any symbols
in the current module.

TEST=Run javascript:alert(new Date().getTimezoneOffset()). It shouldn't return 0 unless you're actually in GMT.
BUG=16800

[Evan Martin, 2009-08-05 22:34:47]

LGTM, style stuff follows

http://codereview.chromium.org/165011/diff/1004/3
File chrome/browser/zygote_main_linux.cc (right):

http://codereview.chromium.org/165011/diff/1004/3#newcode246
Line 246: static bool global_am_zygote_or_renderer = false;
Elsewhere, the "g_" prefix is used for globals.
% git grep '\bg_' -- '*.cc' '*.h' | wc -l
2616

http://codereview.chromium.org/165011/diff/1004/3#newcode287
Line 287: static char timezone_string[64];
Does this need to be static?

http://codereview.chromium.org/165011/diff/1004/3#newcode292
Line 292: typedef struct tm* (*localtime_function) (const time_t* timep);
For types we use CapsLikeThis

this space between parens:  ) (
is weird, here and below.

[agl, 2009-08-05 22:54:01]

(have fixed the other style issues. Will commit tomorrow.)

http://codereview.chromium.org/165011/diff/1004/3
File chrome/browser/zygote_main_linux.cc (right):

http://codereview.chromium.org/165011/diff/1004/3#newcode287
Line 287: static char timezone_string[64];
On 2009/08/05 22:34:47, Evan Martin wrote:
> Does this need to be static?

Sadly, yes. localtime isn't a threadsafe function and returns a pointer to
static data.