Remove som GYP annotations, remove unused manifest.

gpu/gles2_conform_support/native/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# GYP version: gpu/gles2_conform_support/gles2_conform_support.gyp:egl_main_native
 source_set("native") {
   output_name = "egl_main_native"
   sources = [
     "egl_native.cc",
     "main.cc",
   ]
   defines = [
     "GLES2_CONFORM_SUPPORT_ONLY",
     "GTF_GLES20",
     "EGLAPI=",
     "EGLAPIENTRY=",
   ]
   deps = [
     ":windowless",
     "//base",
     "//gpu/gles2_conform_support/egl",
     "//ui/gl",
   ]
   if (is_linux) {
     sources += [
       "egl_native_aura.cc",
       "egl_native_x11.cc",
     ]
   }
   if (is_win) {
     sources += [ "egl_native_win.cc" ]
   }
 }
 
-# GYP version: gpu/gles2_conform_support/gles2_conform_support.gyp:egl_main_windowless
 source_set("windowless") {
   output_name = "egl_main_windowless"
   sources = [
     "egl_native.cc",
     "egl_native_windowless.cc",
     "main.cc",
   ]
   defines = [
     "GLES2_CONFORM_SUPPORT_ONLY",
     "GTF_GLES20",
     "EGLAPI=",
     "EGLAPIENTRY=",
   ]
   deps = [
     "//base",
     "//gpu/gles2_conform_support/egl",
     "//ui/gl",
   ]
 }