Add SkWGLExtensionInterface for dealing with WGL extensions

Add SkWGLExtensionInterface for dealing with WGL extensions
Committed: http://code.google.com/p/skia/source/detail?r=2777

[bsalomon, 2011-12-01 15:06:36]

I want to add support for GLES2 contexts on desktop systems for testing
purposes. Creating a GLES2 context on Windows requires WGL extensions. This
change adds a helper for dealing with WGL extensions.

[TomH, 2011-12-01 15:47:33]

LGTM

http://codereview.appspot.com/5447059/diff/3001/src/utils/win/SkOSWindow_win.cpp
File src/utils/win/SkOSWindow_win.cpp (right):

http://codereview.appspot.com/5447059/diff/3001/src/utils/win/SkOSWindow_win....
src/utils/win/SkOSWindow_win.cpp:285: #include "SkWGL.h"
Should this go at the top of the file with other #includes?

http://codereview.appspot.com/5447059/diff/3001/src/utils/win/SkOSWindow_win....
src/utils/win/SkOSWindow_win.cpp:322: iattrs[15] = samples;
This magic number 15 is overwriting TRUE?

http://codereview.appspot.com/5447059/diff/3001/src/utils/win/SkOSWindow_win....
src/utils/win/SkOSWindow_win.cpp:338: if (0 == format) {
If we don't have multisample, assume we don't have a stencil buffer?

[reed1, 2011-12-01 16:05:32]

http://codereview.appspot.com/5447059/diff/5003/include/utils/SkWGL.h
File include/utils/SkWGL.h (right):

http://codereview.appspot.com/5447059/diff/5003/include/utils/SkWGL.h#newcode76
include/utils/SkWGL.h:76: private:
Now that these are private, you have the option to shorten their names if you
care. e.g.

GetExtensionsStringProc
ChoosePixelFormatProc
...

or just inline the decl. e.g.

const char* (WINAPI* fGetExtensionsString)(HDC);

[reed1, 2011-12-01 16:05:50]

lgtm