Avoid regenerating unchanged bindings files for Dartium.

tools/dom/scripts/multiemitter.py

Index: tools/dom/scripts/multiemitter.py
diff --git a/tools/dom/scripts/multiemitter.py b/tools/dom/scripts/multiemitter.py
index 2e9922c92376369ce15c040383580c6dccbf98dc..e01487c119af8ba024b542c5937ab19df8d774b4 100644
--- a/tools/dom/scripts/multiemitter.py
+++ b/tools/dom/scripts/multiemitter.py
@@ -77,21 +77,29 @@ def _WriteFile(path, lines):
       _logger.info('Mkdir - %s' % dir)
       os.makedirs(dir)
 
-  # Remove file if pre-existing.
+  # If file exists and is unchanged, return.
+  new_contents = ''.join(lines)
   if os.path.exists(path):
-    _logger.info('Removing - %s' % path)
-    os.remove(path)
-    if os.path.exists(path):
-      _logger.info('Warning: File still exists- %s' % path)
+    with open(path) as fd:
+      contents = fd.read()
+    if new_contents == contents:
+      _logger.info('Unchanged file %s' % path)
+      return
+    else:
+      _logger.info('Modified file %s' % path)
+      # Remove old file.
+      _logger.info('Removing - %s' % path)
+      os.remove(path)
+      if os.path.exists(path):
+        _logger.info('Warning: File still exists- %s' % path)

[kustermann, 2013/11/12 11:47:34]

Please remove the whole else part:
- No need to remove the old file, it will be overridden further down anyway.
- No need for the debugging info in that case, we'll get the "Writing (attempt
%)" debugging from line 100.

 
   # Write the file.
   num_attempts = 4
   for i in range(num_attempts):
     try:
       _logger.info('Writing (attempt %d) - %s' % (i + 1, path))
-      f = open(path, 'w')
-      f.writelines(lines)
-      f.close()
+      with open(path, 'w') as fd:
+        fd.write(new_contents)
       return
     except IOError as error:
       last_attempt = (i == (num_attempts - 1))
@@ -114,4 +122,3 @@ def _WriteFile(path, lines):
             _logger.info("Couldn't find %s. Not printing open handles."
                          % handle_file)
         raise error
-