Add SurfaceSequence mojom file to cc/ipc and edit corresponding GYP file

cc/ipc/cc_ipc.gyp

Index: cc/ipc/cc_ipc.gyp
diff --git a/cc/ipc/cc_ipc.gyp b/cc/ipc/cc_ipc.gyp
index 9a7645d1e8ca6bea4e4fedb45a76dd29dc09846f..08c2cef444429fcaf75aa73398dc80b2511e4129 100644
--- a/cc/ipc/cc_ipc.gyp
+++ b/cc/ipc/cc_ipc.gyp
@@ -34,5 +34,25 @@
         'cc_param_traits_macros.h',
       ],
     },
+    {
+      # GN version: //cc/ipc:interfaces
+      # TODO: Add begin_frame_args, render_pass_id, returned_resources and
+      # transferable_resource .mojom and .typemap files here so that this target
+      # is consistent with that in GN build.
+      'target_name': 'interfaces',
+      'type': 'none',
+      'variables': {
+#        'for_blink': 'true',

[ajuma, 2016/06/07 19:16:15]

Should this line be un-commented (do you need this to work with blink types)? Or
can it be removed?

[xlai (Olivia), 2016/06/07 20:45:22]

Just now I did an experiment locally by trying to use cc surface_id in
WebKit/public/ and find that I need both versions of targets: one with
"for_blink=true" and one without "for_blink=true". Mojom generates two sets of
headers, one for blink and one for non-blink. Somehow GN manages to resolve this
automatically, but many GYP build files keep both versions of targets to cover
the difference. 

+        'mojom_files': [
+          'surface_id.mojom',
+          'surface_sequence.mojom',
+        ],
+        'mojom_typemaps': [
+          'surface_id.typemap',
+          'surface_sequence.typemap',
+        ],
+      },
+      'includes': [ '../../mojo/mojom_bindings_generator_explicit.gypi' ],
+    },
   ],
 }