skia: Add support for ANGLE on linux

gyp/common.gypi

 # Copyright 2011 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # This file is automatically included by gyp_skia when building any target.
 
 {
   'includes': [
     'common_variables.gypi',
@@ skipping 12 matching lines @@
     # situations, like building for iOS on a Mac.
     'variables': {
       'conditions': [
         [ 'skia_os != OS and not ((skia_os == "ios" and OS == "mac") or \
                                   (skia_os == "chromeos" and OS == "linux"))', {
           'error': '<!(Cannot build with skia_os=<(skia_os) on OS=<(OS))',
         }],
         [ 'skia_mesa and skia_os not in ["mac", "linux"]', {
           'error': '<!(skia_mesa=1 only supported with skia_os="mac" or "linux".)',
         }],
-        [ 'skia_angle and not skia_os == "win"', {
-          'error': '<!(skia_angle=1 only supported with skia_os="win".)',
+        [ 'skia_angle and not (skia_os == "win" or skia_os == "linux")', {
+          'error': '<!(skia_angle=1 only supported with skia_os="win" or skia_os="linux".)',
         }],
         [ 'skia_os == "chromeos" and OS != "linux"', {
           'error': '<!(Skia ChromeOS build is only supported on Linux.)',
         }],
       ],
     },
     'includes': [
       'common_conditions.gypi',
     ],
     'conditions': [
@@ skipping 53 matching lines @@
           'Release': { 'defines': [ 'NDEBUG' ] },
           'Release_Developer': {
             'inherit_from': ['Release'],
             'defines': [ 'SK_DEVELOPER=1' ],
           },
         },
       }],
     ],
   }, # end 'target_defaults'
 }