Add support for EGL on linux

gyp/gpu.gyp

Index: gyp/gpu.gyp
diff --git a/gyp/gpu.gyp b/gyp/gpu.gyp
index 7bb61f09b6f5509f2934ac1b8632d23c5ee1b9b4..8cf9f76c48c5083ad7a2a77fac4053cb9390fc76 100644
--- a/gyp/gpu.gyp
+++ b/gyp/gpu.gyp
@@ -12,6 +12,7 @@
       }],
       ['skia_os != "linux" and skia_os != "chromeos"', {
         'sources/': [ ['exclude', '_unix.(h|cpp)$'],
+                      ['exclude', 'GrGLCreateNativeInterface_egl.cpp'],
         ],
       }],
       ['skia_os != "ios"', {
@@ -26,6 +27,14 @@
         'sources/': [ ['exclude', '_nacl.(h|cpp)$'],
         ],
       }],
+      ['skia_os == "nacl" or skia_egl == 0', {
+        'sources/': [ ['exclude', '_egl.(h|cpp)$'],
+        ],
+      }],
+      ['skia_egl == 1', {
+        'sources/': [ ['exclude', '_unix.(h|cpp)$'],
+        ],
+      }],
       # nullify the targets in this gyp file if skia_gpu is 0
       [ 'skia_gpu == 0', {
         'sources/': [
@@ -140,6 +149,16 @@
             '../src/gpu/gl/GrGLDefaultInterface_none.cpp',
             '../src/gpu/gl/GrGLCreateNativeInterface_none.cpp',
           ],
+        }],
+        [ '(skia_os == "linux" or skia_os == "chromeos") and skia_egl == 1', {
+          'link_settings': {
+            'libraries': [
+              '-lEGL',
+              '-lGLESv2',
+            ],
+          },
+        }],
+        [ '(skia_os == "linux" or skia_os == "chromeos") and skia_egl == 0', {
           'link_settings': {
             'libraries': [
               '-lGL',
@@ -155,6 +174,11 @@
             ],
           },
         }],
+        [ 'skia_egl==1', {
+          'defines': [
+            'SK_EGL',
+          ],
+        }],
         [ 'skia_mesa and skia_os == "linux"', {
           'link_settings': {
             'libraries': [