Add copyright headers to remaining gyp files.

gyp/angle.gyp

+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
 # ANGLE is the Windows-specific translator from OGL ES to D3D
 
 {
   'targets': [
     {
       'target_name': 'angle',
       'type': 'none',
       'conditions': [
         [ 'skia_angle', {
           'direct_dependent_settings': {
             'include_dirs': [
               '../third_party/externals/angle2/include',
             ],
           },
           'dependencies': [
             '../third_party/externals/angle2/src/angle.gyp:libEGL',
             '../third_party/externals/angle2/src/angle.gyp:libGLESv2',
           ],
         }],
       ],
     },
   ],
 }