Make EventInterfaces.in build step not depend on bindings generation

Source/bindings/core_bindings_generated.gyp

+# Copyright 2014 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.
+
+# Generate EventInterfaces.in, used by core/ but depends on modules/,
+# hence placed in bindings/ to avoid direct core/ -> modules/ dependency.
+
+{
+  'includes': [
+    'bindings.gypi',
+    '../core/core.gypi',
+    '../modules/modules.gypi',
+  ],
+
+  'targets': [
+  {
+    'target_name': 'core_bindings_generated',
+    'type': 'none',
+    'actions': [
+      {
+        'action_name': 'event_interfaces',
+        'variables': {
+          'event_idl_files': [
+            '<@(core_event_idl_files)',
+            '<@(modules_event_idl_files)',
+          ],
+          'event_idl_files_list':
+              '<|(event_idl_files_list.tmp <@(event_idl_files))',
+        },
+        'inputs': [
+          '../bindings/scripts/generate_event_interfaces.py',
+          '../bindings/scripts/utilities.py',
+          '<@(event_idl_files)',
+        ],
+        'outputs': [
+          '<(blink_output_dir)/EventInterfaces.in',
+        ],
+        'action': [
+          'python',
+          '../bindings/scripts/generate_event_interfaces.py',
+          '--event-idl-files-list',
+          '<(event_idl_files_list)',
+          '--event-interfaces-file',
+          '<(blink_output_dir)/EventInterfaces.in',
+          '--write-file-only-if-changed',
+          '<(write_file_only_if_changed)',
+        ],
+      },
+    ],
+  },
+  ],  # targets
+}