Make it possible to use OSMesa on Android

ui/gl/gl.gyp

Index: ui/gl/gl.gyp
diff --git a/ui/gl/gl.gyp b/ui/gl/gl.gyp
index 95db80957d81b3e009e91af85127ca39d6919007..54c3eaa9474174e6c04faf33e7026447603515d0 100644
--- a/ui/gl/gl.gyp
+++ b/ui/gl/gl.gyp
@@ -264,6 +264,8 @@
           'sources': [
             'gl_image_egl.cc',
             'gl_image_egl.h',
+            'gl_implementation_linux.cc',
+            'gl_implementation_linux.h',

[Peter Beverloo, 2013/10/03 19:46:42]

I've tried a ton of things (regular inclusions like this, sources/ include
expressions) to get gl_implementation_linux.cc to be included in Android's
target, but it doesn't want to work.

Does anyone know the gyp structure in ui/gl/ who can understand why a normal
override of the OS-specific regexp (filename_rules.gypi:32) doesn't work here? 
I should be able to use:

'sources/': [
  ['include', 'gl_implementation_linux\\.cc$'],
],

but that doesn't work (tried with a full path, no escaping, regexp for (cc|h),
and so on)...

[piman, 2013/10/03 19:54:18]

Not sure... Feel free to rename this (though I can't come up with a good name),
and add it explicitly on linux/android.

           ],
           'link_settings': {
             'libraries': [
@@ -271,7 +273,6 @@
             ],
           },
           'sources!': [
-            'gl_context_osmesa.cc',
             'system_monitor_posix.cc',
           ],
           'defines': [