cc: Add PRESUBMIT check for passing simple gfx types by value.

cc/PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for cc.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into gcl.
 """
 
 import re
+import string
 
 CC_SOURCE_FILES=(r'^cc/.*\.(cc|h)$',)
 CC_PERF_TEST =(r'^.*_perftest.*\.(cc|h)$',)
 
 def CheckChangeLintsClean(input_api, output_api):
   input_api.cpplint._cpplint_state.ResetErrorCounts()  # reset global state
   source_filter = lambda x: input_api.FilterSourceFile(
     x, white_list=CC_SOURCE_FILES, black_list=None)
   files = [f.AbsoluteLocalPath() for f in
            input_api.AffectedSourceFiles(source_filter)]
@@ skipping 27 matching lines @@
   if assert_files:
     return [output_api.PresubmitError(
       'These files use ASSERT instead of using DCHECK:',
       items=assert_files)]
   if notreached_files:
     return [output_api.PresubmitError(
       'These files use ASSERT_NOT_REACHED instead of using NOTREACHED:',
       items=notreached_files)]
   return []
 
-def CheckSpamLogging(input_api, output_api, white_list=CC_SOURCE_FILES, black_list=None):
+def CheckSpamLogging(input_api,
+                     output_api,
+                     white_list=CC_SOURCE_FILES,
+                     black_list=None):
   black_list = tuple(black_list or input_api.DEFAULT_BLACK_LIST)
-  source_file_filter = lambda x: input_api.FilterSourceFile(x, white_list, black_list)
+  source_file_filter = lambda x: input_api.FilterSourceFile(x,
+                                                            white_list,
+                                                            black_list)
 
   log_info = []
   printf = []
 
   for f in input_api.AffectedSourceFiles(source_file_filter):
     contents = input_api.ReadFile(f, 'rb')
     if re.search(r"\bD?LOG\s*\(\s*INFO\s*\)", contents):
       log_info.append(f.LocalPath())
     if re.search(r"\bf?printf\(", contents):
       printf.append(f.LocalPath())
 
   if log_info:
     return [output_api.PresubmitError(
       'These files spam the console log with LOG(INFO):',
       items=log_info)]
   if printf:
     return [output_api.PresubmitError(
       'These files spam the console log with printf/fprintf:',
       items=printf)]
   return []
 
+def CheckPassByValue(input_api,
+                     output_api,
+                     white_list=CC_SOURCE_FILES,
+                     black_list=None):
+  black_list = tuple(black_list or input_api.DEFAULT_BLACK_LIST)
+  source_file_filter = lambda x: input_api.FilterSourceFile(x,
+                                                            white_list,
+                                                            black_list)
+
+  local_errors = []
+
+  # Well-defined simple classes containing only <= 4 ints, or <= 2 floats.
+  pass_by_value_types = ['base::Time',
+                         'base::TimeTicks',
+                         'gfx::Point',
+                         'gfx::PointF',
+                         'gfx::Rect',
+                         'gfx::Size',
+                         'gfx::SizeF',
+                         'gfx::Vector2d',
+                         'gfx::Vector2dF',
+                         ]
+
+  for f in input_api.AffectedSourceFiles(source_file_filter):
+    contents = input_api.ReadFile(f, 'rb')
+    match = re.search(
+      r'\bconst +' + '(?P<type>(%s))&' %
+        string.join(pass_by_value_types, '|'),
+      contents)
+    if match:
+      local_errors.append(output_api.PresubmitError(
+        '%s passes %s by const ref instead of by value.' %
+        (f.LocalPath(), match.group('type'))))
+  return local_errors
 
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results += CheckAsserts(input_api, output_api)
   results += CheckSpamLogging(input_api, output_api, black_list=CC_PERF_TEST)
+  results += CheckPassByValue(input_api, output_api)
   results += CheckChangeLintsClean(input_api, output_api)
   return results
 
 def GetPreferredTrySlaves(project, change):
   return [
     'linux_layout_rel',
     ]