Add presubmit check for correct MessageLoopProxy usage in src/media/.

media/PRESUBMIT.py

Index: media/PRESUBMIT.py
diff --git a/media/PRESUBMIT.py b/media/PRESUBMIT.py
index aafe23a2f9fd19fd482c762d878ebdb48ae43014..ced9069008213df5900cf6076fcf0bc0f7f2387e 100644
--- a/media/PRESUBMIT.py
+++ b/media/PRESUBMIT.py
@@ -8,15 +8,15 @@ See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
+def _FilterFile(affected_file):
+  """Return true if the file could contain code requiring a presubmit check."""
+  return affected_file.LocalPath().endswith(
+      ('.h', '.cc', '.cpp', '.cxx', '.mm'))
+
 
 def _CheckForUseOfWrongClock(input_api, output_api):
   """Make sure new lines of media code don't use a clock susceptible to skew."""
 
-  def FilterFile(affected_file):
-    """Return true if the file could contain code referencing base::Time."""
-    return affected_file.LocalPath().endswith(
-        ('.h', '.cc', '.cpp', '.cxx', '.mm'))
-
   # Regular expression that should detect any explicit references to the
   # base::Time type (or base::Clock/DefaultClock), whether in using decls,
   # typedefs, or to call static methods.
@@ -45,7 +45,7 @@ def _CheckForUseOfWrongClock(input_api, output_api):
       r'(' + using_base_time_decl_pattern + r')|(' +
       base_time_konstant_pattern + r')')
   problems = []
-  for f in input_api.AffectedSourceFiles(FilterFile):
+  for f in input_api.AffectedSourceFiles(_FilterFile):
     for line_number, line in f.ChangedContents():
       if problem_re.search(line):
         if not exception_re.search(line):
@@ -63,16 +63,38 @@ def _CheckForUseOfWrongClock(input_api, output_api):
   else:
     return []
 
+def _CheckForMessageLoopProxy(input_api, output_api):
+  """Make sure media code only uses MessageLoopProxy for accessing the current

[DaleCurtis, 2014/01/07 20:00:42]

I'm not sure what you mean here.  Can you elaborate?  There's only a single
static on MessageLoopProxy... current() -- What else do you expect this to
catch?

[scherkus (not reviewing), 2014/01/07 20:06:10]

we want to catch any use of MessageLoopProxy that isn't
MessageLoopProxy::current()

For example:

void ShouldBeUsingTaskRunner(const scoped_refptr<MessageLoopProxy>& loop);

class Blah {
  scoped_refptr<MessageLoopProxy> should_be_a_task_runner_;
};

[DaleCurtis, 2014/01/07 20:13:46]

Are you expecting SingleThreadTaskRunner or TaskRunner?  Either way, I think you
need a more elaborate error message when these cases are detected so users w/
errors have an idea of what to do to fix their problem.

[scherkus (not reviewing), 2014/01/07 21:40:22]

I'm expecting anything other than MLP, but in most cases STTR.

I reworked the message -- let me know what you think.

+  loop."""
+
+  message_loop_proxy_re = r'\bMessageLoopProxy(::current\(\))?'
+
+  bad_files = []
+  for f in input_api.AffectedSourceFiles(_FilterFile):
+    contents = input_api.ReadFile(f, 'rb')
+    for match in input_api.re.finditer(message_loop_proxy_re, contents):
+      if match.lastindex == 1:
+        continue
+
+      # No need to check remaining matches in an offending file.
+      bad_files.append(f)
+      break
+
+  if bad_files:
+    return [output_api.PresubmitError(
+      'These files reference MessageLoopProxy for uses other than accessing '
+      'the current loop:', bad_files)]
+
+  return []
 
 def _CheckChange(input_api, output_api):
   results = []
   results.extend(_CheckForUseOfWrongClock(input_api, output_api))
+  results.extend(_CheckForMessageLoopProxy(input_api, output_api))
   return results
 
-

[DaleCurtis, 2014/01/07 20:00:42]

Python style is two lines between global methods.

[scherkus (not reviewing), 2014/01/07 20:06:10]

whoops! done

 def CheckChangeOnUpload(input_api, output_api):
   return _CheckChange(input_api, output_api)
 
-
 def CheckChangeOnCommit(input_api, output_api):
   return _CheckChange(input_api, output_api)