Convert from using env['PLATFORM'] directly to using the more flexible...

Convert from using env['PLATFORM'] directly to using the more flexible
and better-thought-out Hammer env.Bits() idioms:
* env['PLATFORM'] == 'win32' => env.Bit('windows')
* env['PLATFORM'] == 'posix' => env.Bit('linux')
* env['PLATFORM'] == 'darwin' => env.Bit('mac')
New idioms:
* env.Bit('posix') => really does mean "any POSIX platform"
* env.AnyBits('mac', 'linux') => specifically mac or linux, excluding
  other POSIX platforms
Where we were using compound conditionals (e.g., "env['PLATFORM'] in
('posix', 'darwin')") I tried to take my best shot at translating
the intent (i.e., "env.Bits('posix')" for something POSIX, "not
env.Bits('mac')" for something not yet ported to Mac, etc.)

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=7270

[sgk, 2008-12-18 22:05:22]

Generating Visual Studio files (regardless of what platform you're running on)
and eventually XCode files will use the Hammer env.Bit() idioms to get the
appropriate list of Windows sources files even when you're running on another
platform.  So now's as good a time as any to cut over (nearly) all the SCons
config to using env.Bit().

Biggest semantic change:  the old env['PLATFORM'] == 'posix' test really meant
"are we building on linux?" (because SCons got this wrong originally) wherease
the new env.Bit('posix') test really does mean "are we building on any POSIX
system?".  env.Bit('linux') and env.Bit('mac') mean what you'd expect.

I didn't convert gears (since that part's not been hammerized) or
third_party/WebKit (since cygwin is still muddying those waters for now).

[bradn, 2008-12-18 22:32:07]

LGTM

[tony, 2008-12-18 22:47:40]

If everything builds, rubber stamp, LGTM!