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..b13b47526759fabc69129509026a6b7b6791e3b9 100644
--- a/gyp/common_variables.gypi
+++ b/gyp/common_variables.gypi
@@ -50,6 +50,7 @@
         'skia_arch_type%': 'x86',
         'arm_version%': 0,
         'arm_neon%': 0,
+        'skia_egl%': 0,
       },
 
       # Re-define all variables defined within the level-3 'variables' dict,
@@ -59,6 +60,7 @@
       'skia_arch_type%': '<(skia_arch_type)',
       'arm_version%': '<(arm_version)',
       'arm_neon%': '<(arm_neon)',
+      'skia_egl%': '<(skia_egl)',
 
       'conditions': [
         [ 'skia_android_framework == 1', {
@@ -87,6 +89,7 @@
         }],
         [ 'skia_os == "android"', {
           'skia_static_initializers%': 0,
+          'skia_egl%': 1,
         }, {
           'skia_static_initializers%': 1,
         }],
@@ -95,6 +98,9 @@
           'arm_version%': 7,
           'arm_neon%': 0, # neon asm files known not to work with the ios build
         }],
+        [ 'skia_os in "nacl"', {
+          'skia_egl%': 1,
+        }],
         [ 'skia_os in ["android", "nacl"] and not skia_android_framework',
           # skia_freetype_static - on OS variants that normally would
           #     dynamically link the system FreeType library, don't do
@@ -233,6 +239,7 @@
     '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)
     #