Add a presubmit check to look for duplicate Valgrind/Heapchecker suppression name...

tools/valgrind/memcheck/PRESUBMIT.py

 # Copyright (c) 2010 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.
 
 """
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details on the presubmit API built into gcl.
 """
 
 def CheckChange(input_api, output_api):
   """Checks the memcheck suppressions files for bad data."""
+  suppressions = {}
   errors = []
+  # skip_next_line has 3 possible values:
+  # - False: don't skip the next line.
+  # - 'skip_suppression_name': the next line is a suppression name, skip.
+  # - 'skip_param': the next line is a system call parameter error, skip.
   skip_next_line = False
   func_re = input_api.re.compile('[a-z_.]+\(.+\)$')
   for f, line_num, line in input_api.RightHandSideLines(lambda x:
       x.LocalPath().endswith('.txt')):
     line = line.lstrip()
     if line.startswith('#') or not line:
       continue
 
     if skip_next_line:
+      if skip_next_line == 'skip_suppression_name':
+        if suppressions.has_key(line):
+          errors.append('suppression with name "%s" at %s line %s has already '
+                        'been defined at line %s' % (line, f.LocalPath(),
+                                                     line_num,
+                                                     suppressions[line][1]))
+        else:
+          suppressions[line] = (f, line_num)
       skip_next_line = False
       continue
-    if line == '{' or line == "Memcheck:Param":
-      skip_next_line = True
+    if line == '{':
+      skip_next_line = 'skip_suppression_name'
       continue
+    if line == "Memcheck:Param":
+      skip_next_line = 'skip_param'
+      continue
+
     if (line.startswith('fun:') or line.startswith('obj:') or
         line.startswith('Memcheck:') or line == '}' or
         line == '...'):
       continue
     if func_re.match(line):
       continue
     errors.append('"%s" is probably wrong: %s line %s' % (line, f.LocalPath(),
                                                           line_num))
   if errors:
     return [output_api.PresubmitError('\n'.join(errors))]
   return []
 
 def CheckChangeOnUpload(input_api, output_api):
   return CheckChange(input_api, output_api)
 
 def CheckChangeOnCommit(input_api, output_api):
   return CheckChange(input_api, output_api)
 
 def GetPreferredTrySlaves():
   return ['linux_valgrind', 'mac_valgrind']