Bindings build: split compute_interfaces_info into 2 stages

Source/bindings/scripts/utilities.py

 # 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.
 
 """Utility functions (file reading, simple IDL parsing by regexes) for IDL build.
 
 Design doc: http://www.chromium.org/developers/design-documents/idl-build
 """
 
 import os
@@ skipping 21 matching lines @@
         with open(destination_filename) as destination_file:
             if destination_file.read() == new_text:
                 return
     with open(destination_filename, 'w') as destination_file:
         destination_file.write(new_text)
 
 
 def write_pickle_file(pickle_filename, data, only_if_changed):
     if only_if_changed and os.path.isfile(pickle_filename):
         with open(pickle_filename) as pickle_file:
-            if pickle.load(pickle_file) == data:
-                return
+            try:
+                if pickle.load(pickle_file) == data:
+                    return
+            except (EOFError, pickle.UnpicklingError):
+                # If trouble unpickling, overwrite
+                pass
     with open(pickle_filename, 'w') as pickle_file:
         pickle.dump(data, pickle_file)
 
 
 ################################################################################
 # IDL parsing
 #
 # We use regular expressions for parsing; this is incorrect (Web IDL is not a
 # regular language), but simple and sufficient in practice.
 # Leading and trailing context (e.g. following '{') used to avoid false matches.
@@ skipping 87 matching lines @@
 
 def get_put_forward_interfaces_from_idl(file_contents):
     put_forwards_pattern = (r'\[[^\]]*PutForwards=[^\]]*\]\s+'
                             r'readonly\s+'
                             r'attribute\s+'
                             r'(\w+)')
     return sorted(set(match.group(1)
                       for match in re.finditer(put_forwards_pattern,
                                                file_contents,
                                                flags=re.DOTALL)))