Added gyp build rules for brotli.

third_party/brotli/bro.gypi

+# Copyright (c) 2016 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.
+
+# Usage:
+# {
+#   'target_name': 'your_target_name',
+#   'type': 'none',
+#   'actions': [
+#     {
+#       'variables': {
+#         'input_file': 'file/to/compress',
+#         'output_file': 'file/to/put/compressed',
+#       },
+#       'includes': ['../third_party/brotli/bro.gypi'],
+#     }
+#   ],
+#   'dependencies': [
+#     'path/to:builds_file_to_compress'
+#   ],
+# },
+
+{
+  'action_name': 'genbro',
+  'variables': {
+    'bro': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)bro<(EXECUTABLE_SUFFIX)',
+  },
+  'inputs': [
+    '<(bro)',
+    '<(input_file)',
+  ],
+  'outputs': [
+    '<(output_file)',
+  ],
+  'action': [
+    '<(bro)',
+    '--force',
+    '--input',
+    '<(input_file)',
+    '--output',
+    '<(output_file)',
+  ],
+  'dependencies': [
+    '<(DEPTH)/third_party/brotli/brotli.gyp:bro',
+  ],
+}