Add empty dart:platform library.

Add empty dart:platform library.

dart:platform will be a library that contains information about the runtime
platform. While it's not written in stones, this is examples of properties that
may be queried:

- OS
- Browser
- Browser version
- Dart Version
- numberOfProcessors
- pathSeparator
- Native or JS VM

BUG=
R=ahe@google.com, asiva@google.com, floitsch@google.com, iposva@google.com, kasperl@google.com

Committed: https://code.google.com/p/dart/source/detail?r=29154

[ahe, 2013-10-21 14:38:59]

I can't spot any flaws in the dart2js changes, but could you elaborate a bit on
what this library is for?

[Anders Johnsen, 2013-10-21 14:45:51]

Sure thing, Peter:

dart:platform will be a library that contains information about the runtime
platform. While it's not written in stones, this is examples of properties that
may be queried:

- OS
- Browser
- Browser version
- Dart Version
- numberOfProcessors
- pathSeparator
- Native or JS VM

[ahe, 2013-10-21 14:46:41]

Anything not in runtime, LGTM!

[floitsch, 2013-10-21 14:56:36]

LGTM.

[Ivan Posva, 2013-10-22 00:19:53]

On 2013/10/21 14:45:51, Anders Johnsen wrote:
> Sure thing, Peter:
> 
> dart:platform will be a library that contains information about the runtime
> platform. While it's not written in stones, this is examples of properties
that
> may be queried:
> 
> - OS
> - Browser
> - Browser version
> - Dart Version
> - numberOfProcessors
> - pathSeparator
> - Native or JS VM

Why is the path separator not part of dart:io? As far as I can tell it should
only be needed to deal with IO functionality to open files. URI paths do always
use '/' to separate path elements so it should not be needed anywhere else.

Thanks,
-Ivan

[Anders Johnsen, 2013-10-22 05:23:23]

As said above, the list is not set in stones. It's purely to get the idea of
what we're considering to add. There'll be follow-up CLs for each change going
in here. I agree that it's 'pathSeparator' is less clear, but it's something
that will have to be discussed.

[kasperl, 2013-10-22 06:20:13]

LGTM.

[ahe, 2013-10-22 09:34:03]

On 2013/10/22 00:19:53, Ivan Posva wrote:
> Why is the path separator not part of dart:io? As far as I can tell it should
> only be needed to deal with IO functionality to open files. URI paths do
always
> use '/' to separate path elements so it should not be needed anywhere else.

I had assumed path separator would be ":" or ";". However, that doesn't really
seem useful in Dart.

There is no need to have a concept to model "/" vs "\\". Uri.file already takes
care of that, much better than you can do with just a separator character.

[Cutch, 2013-10-22 10:15:13]

I would like to add some SIMD acceleration flags here too.

[siva, 2013-10-22 16:18:01]

The io library already sems to have a Platform class, are you
planning on moving some of that code out of dart:io?

[floitsch, 2013-10-22 16:26:32]

On 2013/10/22 16:18:01, siva wrote:
> The io library already sems to have a Platform class, are you
> planning on moving some of that code out of dart:io?

yes.

[Anders Johnsen, 2013-10-22 19:43:00]

FYI, I'll land this CL as soon as I get a lgtm from the VM team.

[siva, 2013-10-22 22:36:04]

The changes in general LGTM, there was one question from Ivan about why this
needed to be separate library and not just a class in dart:core.

[Ivan Posva, 2013-10-23 04:34:07]

I am failing to see the reason for adding a whole new library only to hold one
or two handful of getters.

Florian, Anders, please explain before committing as it is really hard to accept
this addition without seeing examples of how the different  values will be
exposed.

Thanks,
-Ivan

[Ivan Posva, 2013-10-24 00:26:07]

Florian,

Thanks for the explanations.

LGTM, but now we need to add some meat into this library.

-Ivan

[Anders Johnsen, 2013-10-24 06:56:49]

Committed patchset #1 manually as r29154 (presubmit successful).