Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

gpu/gles2_conform_support/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.
 
 declare_args() {
   # Set to true to compile with the OpenGL ES 2.0 conformance tests.
   internal_gles2_conform_tests = false
 }
 
 config("gles2_conform_test_warnings") {
@@ skipping 452 matching lines @@
     #         ],
     #       }],
     #     ],
     #    },
   }
 }
 
 test("gles2_conform_test") {
   sources = [
     "gles2_conform_test.cc",
+    "gles2_conform_test.h",
   ]
   deps = [
     "//base",
     "//base/test:test_support",
     "//gpu/config",
     "//testing/gtest",
   ]
 
   data = [
     "gles2_conform_test_expectations.txt",
   ]
 
   if (internal_gles2_conform_tests) {
     data_deps = [
       ":gles2_conform_test_windowless",
     ]
     deps += [ ":generate_gles2_conform_tests" ]
     sources += [ "$target_gen_dir/gles2_conform_test_autogen.cc" ]
     data += [ "//third_party/gles2_conform/GTF_ES/" ]
   }
 }