Add support for EGL on linux

gyp/common_variables.gypi

Index: gyp/common_variables.gypi
diff --git a/gyp/common_variables.gypi b/gyp/common_variables.gypi
index 6d791c91523534ab2cd74758a7519c354634d5e9..bf4227f09f1c21a1135cb7f5f57438f6d1080b82 100644
--- a/gyp/common_variables.gypi
+++ b/gyp/common_variables.gypi
@@ -65,10 +65,12 @@
           'skia_os%': 'android',
           'skia_chrome_utils%': 0,
           'skia_use_system_json%': 1,
+          'skia_egl%': 1,
         }, {
           'skia_os%': '<(skia_os)',
           'skia_chrome_utils%': 1,
           'skia_use_system_json%': 0,
+          'skia_egl%': 0,
         }],
         [ 'skia_os == "win"', {
           'os_posix%': 0,
@@ -233,6 +235,7 @@
     'skia_disable_inlining%': 0,
     'skia_moz2d%': 0,
     'skia_is_bot%': '<!(python -c "import os; print os.environ.get(\'CHROME_HEADLESS\', 0)")',
+    'skia_egl%': '<(skia_egl)',
 
     # These are referenced by our .gypi files that list files (e.g. core.gypi)
     #