llvm-coverage script: respect SKIA_OUT

tools/llvm_coverage_run.py

 #!/usr/bin/env python
 # Copyright (c) 2015 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.
 
 
 """Run the given command through LLVM's coverage tools."""
 
 
 import argparse
 import json
 import os
 import re
 import shlex
 import subprocess
 import sys
 
 
 BUILDTYPE = 'Coverage'
-OUT_DIR = os.path.realpath(os.path.join('out', BUILDTYPE))
+DEFAULT_OUT_DIR = os.path.realpath(os.path.join('out', BUILDTYPE))
 PROFILE_DATA = 'default.profraw'
 PROFILE_DATA_MERGED = 'prof_merged'
+SKIA_OUT = 'SKIA_OUT'
 
 
 def _fix_filename(filename):
   """Return a filename which we can use to identify the file.
 
   The file paths printed by llvm-cov take the form:
 
       /path/to/repo/out/dir/../../src/filename.cpp
 
   And then they're truncated to 22 characters with leading ellipses:
@@ skipping 27 matching lines @@
         matched.append(f)
     if len(matched) == 1:
       filtered.append((percent, matched[0]))
     elif len(matched) > 1:
       print >> sys.stderr, ('WARNING: multiple matches for %s; skipping:\n\t%s'
                             % (new_file, '\n\t'.join(matched)))
   print 'Filtered out %d files.' % (len(results) - len(filtered))
   return filtered
 
 
+def _get_out_dir():
+  """Determine the location for compiled binaries."""
+  if os.environ.get(SKIA_OUT):

[mtklein, 2015/07/15 14:30:46]

I think we can be pithier and just as clear:
  return os.path.join(os.environ.get('SKIA_OUT', 'out'), 'Coverage')

[borenet, 2015/07/15 14:42:02]

Done.

+    return os.path.join(os.environ[SKIA_OUT], BUILDTYPE)
+  return DEFAULT_OUT_DIR
+
+
 def run_coverage(cmd):
   """Run the given command and return per-file coverage data.
 
   Assumes that the binary has been built using llvm_coverage_build and that
   LLVM 3.6 or newer is installed.
   """
-  binary_path = os.path.join(OUT_DIR, cmd[0])
+  binary_path = os.path.join(_get_out_dir(), cmd[0])
   subprocess.call([binary_path] + cmd[1:])
   try:
     subprocess.check_call(
         ['llvm-profdata', 'merge', PROFILE_DATA,
          '-output=%s' % PROFILE_DATA_MERGED])
   finally:
     os.remove(PROFILE_DATA)
   try:
     report = subprocess.check_output(
         ['llvm-cov', 'report', '-instr-profile', PROFILE_DATA_MERGED,
@@ skipping 79 matching lines @@
   format_results = _nanobench_json(results, properties, key)
   if args.outResultsFile:
     with open(args.outResultsFile, 'w') as f:
       json.dump(format_results, f)
   else:
     print json.dumps(format_results, indent=4, sort_keys=True)
 
 
 if __name__ == '__main__':
   main()