[SysApps] Expose ffmpeg function signatures needed by Device Capabili…

…ties API

We need these functions in to get the list of Codecs available in the
system for getAVCodecs(). If we ever fork ffmpeg, we can just remove
this patch and add the signatures directly at the ffmpeg's signature
list.

tools/generate_stubs/generate_stubs.py

@@ -382,7 +382,7 @@ def ExtractModuleName(infile_path):
   return basename
 
 
-def ParseSignatures(infile):
+def ParseSignaturesReal(infile):
   """Parses function signatures in the input file.
 
   This function parses a file of signatures into a list of dictionaries that
@@ -426,6 +426,27 @@ def ParseSignatures(infile):
   return signatures
 
 
+# Sometimes additional signatures other than what is exposed to Chromium are
+# needed, in particular for ffmpeg. If we ever make a fork of ffmpeg, is
+# probably a good idea to remove this patch and add the signatures directly on
+# the .sigs file at the dependency repository. In order to expose additional
+# signatures of a library foobar, just add a .sig file prefixed with "xwalk_" at
+# the root folder of the directory containing this script.
+def ParseSignatures(infile):
+  signatures = ParseSignaturesReal(infile)
+
+  xwalk_sig_dir = os.path.dirname(os.path.realpath(__file__))
+  xwalk_sig_file = os.path.join(xwalk_sig_dir,
+                                'xwalk_' + os.path.basename(infile.name))
+
+  if os.path.exists(xwalk_sig_file):
+    xwalk_infile = open(xwalk_sig_file, 'r')
+    signatures += ParseSignaturesReal(xwalk_infile)
+    xwalk_infile.close()
+
+  return signatures
+
+
 def WriteWindowsDefFile(module_name, signatures, outfile):
   """Writes a windows def file to the given output file object.
 

tools/generate_stubs/xwalk_ffmpegsumo.sigs

@@ -0,0 +1,7 @@
+# Copyright (c) 2013 Intel Corporation. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+AVCodec *av_codec_next(const AVCodec *c);
+int av_codec_is_encoder(const AVCodec *c);
+int av_codec_is_decoder(const AVCodec *c);