Add support for EGL on linux

gyp/gpu.gypi

 # Include this gypi to include all 'gpu' files
 # The parent gyp/gypi file must define
 #       'skia_src_path'     e.g. skia/trunk/src
 #       'skia_include_path' e.g. skia/trunk/include
 #
 # The skia build defines these in common_variables.gypi
 #
 {
   'variables': {
     'skgpu_sources': [
@@ skipping 279 matching lines @@
       '<(skia_src_path)/image/SkImage_Gpu.cpp',
       '<(skia_src_path)/image/SkSurface_Gpu.cpp',
 
       '<(skia_src_path)/gpu/gl/SkGLContextHelper.cpp'
     ],
     'skgpu_native_gl_sources': [
       '<(skia_src_path)/gpu/gl/GrGLDefaultInterface_native.cpp',
       '<(skia_src_path)/gpu/gl/mac/GrGLCreateNativeInterface_mac.cpp',
       '<(skia_src_path)/gpu/gl/win/GrGLCreateNativeInterface_win.cpp',
       '<(skia_src_path)/gpu/gl/unix/GrGLCreateNativeInterface_unix.cpp',
+      '<(skia_src_path)/gpu/gl/egl/GrGLCreateNativeInterface_egl.cpp',
       '<(skia_src_path)/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp',
       '<(skia_src_path)/gpu/gl/android/GrGLCreateNativeInterface_android.cpp',
 
       # Sk files
       '<(skia_include_path)/gpu/gl/SkNativeGLContext.h',
       '<(skia_src_path)/gpu/gl/mac/SkNativeGLContext_mac.cpp',
       '<(skia_src_path)/gpu/gl/nacl/SkNativeGLContext_nacl.cpp',
       '<(skia_src_path)/gpu/gl/win/SkNativeGLContext_win.cpp',
       '<(skia_src_path)/gpu/gl/unix/SkNativeGLContext_unix.cpp',
-      '<(skia_src_path)/gpu/gl/android/SkNativeGLContext_android.cpp',
+      '<(skia_src_path)/gpu/gl/egl/SkNativeGLContext_egl.cpp',
       '<(skia_src_path)/gpu/gl/iOS/SkNativeGLContext_iOS.mm',
     ],
     'skgpu_mesa_gl_sources': [
       '<(skia_src_path)/gpu/gl/mesa/GrGLCreateMesaInterface.cpp',
 
       # Sk files
       '<(skia_include_path)/gpu/gl/SkMesaGLContext.h',
       '<(skia_src_path)/gpu/gl/mesa/SkMesaGLContext.cpp',
     ],
     'skgpu_angle_gl_sources': [
@@ skipping 30 matching lines @@
     ],
     'skgpu_null_gl_sources': [
       '<(skia_src_path)/gpu/gl/GrGLCreateNullInterface.cpp',
 
       # Sk files
       '<(skia_include_path)/gpu/gl/SkNullGLContext.h',
       '<(skia_src_path)/gpu/gl/SkNullGLContext.cpp',
     ],
   },
 }