Add --src-dir flag to landmines.py.

This will make it possible to reuse the script in projects
with different directory layouts than Chromium, since the
current version assumes the root is two levels above the
script location.

BUG=webrtc:5077
TESTED=Manually running the script and running runhooks.

Review URL: https://codereview.chromium.org/1407733002

Cr-Original-Commit-Position: refs/heads/master@{#354083}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 20b291561ce84495d9af94b5cc7f0cb9765d128c

landmines.py

@@ -27,10 +27,7 @@ import clobber
 import landmine_utils
 
 
-SRC_DIR = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
-
-
-def get_build_dir(build_tool, is_iphone=False):
+def get_build_dir(build_tool, src_dir, is_iphone=False):
   """
   Returns output directory absolute path dependent on build and targets.
   Examples:
@@ -42,7 +39,7 @@ def get_build_dir(build_tool, is_iphone=False):
   """
   ret = None
   if build_tool == 'xcode':
-    ret = os.path.join(SRC_DIR, 'xcodebuild')
+    ret = os.path.join(src_dir, 'xcodebuild')
   elif build_tool in ['make', 'ninja', 'ninja-ios']:  # TODO: Remove ninja-ios.
     if 'CHROMIUM_OUT_DIR' in os.environ:
       output_dir = os.environ.get('CHROMIUM_OUT_DIR').strip()
@@ -50,16 +47,16 @@ def get_build_dir(build_tool, is_iphone=False):
         raise Error('CHROMIUM_OUT_DIR environment variable is set but blank!')
     else:
       output_dir = landmine_utils.gyp_generator_flags().get('output_dir', 'out')
-    ret = os.path.join(SRC_DIR, output_dir)
+    ret = os.path.join(src_dir, output_dir)
   else:
     raise NotImplementedError('Unexpected GYP_GENERATORS (%s)' % build_tool)
   return os.path.abspath(ret)
 
 
-def clobber_if_necessary(new_landmines):
+def clobber_if_necessary(new_landmines, src_dir):
   """Does the work of setting, planting, and triggering landmines."""
-  out_dir = get_build_dir(landmine_utils.builder())
-  landmines_path = os.path.normpath(os.path.join(out_dir, '..', '.landmines'))
+  out_dir = get_build_dir(landmine_utils.builder(), src_dir)
+  landmines_path = os.path.normpath(os.path.join(src_dir, '.landmines'))
   try:
     os.makedirs(out_dir)
   except OSError as e:
@@ -85,14 +82,16 @@ def clobber_if_necessary(new_landmines):
 
 
 def process_options():
-  """Returns a list of landmine emitting scripts."""
+  """Returns an options object containing the configuration for this script."""
   parser = optparse.OptionParser()
   parser.add_option(
       '-s', '--landmine-scripts', action='append',
-      default=[os.path.join(SRC_DIR, 'build', 'get_landmines.py')],
       help='Path to the script which emits landmines to stdout. The target '
            'is passed to this script via option -t. Note that an extra '
            'script can be specified via an env var EXTRA_LANDMINES_SCRIPT.')
+  parser.add_option('-d', '--src-dir',
+      help='Path of the source root dir. Overrides the default location of the '
+           'source root dir when calculating the build directory.')
   parser.add_option('-v', '--verbose', action='store_true',
       default=('LANDMINES_VERBOSE' in os.environ),
       help=('Emit some extra debugging information (default off). This option '
@@ -107,15 +106,27 @@ def process_options():
   logging.basicConfig(
       level=logging.DEBUG if options.verbose else logging.ERROR)
 
+  if options.src_dir:
+    if not os.path.isdir(options.src_dir):
+      parser.error('Cannot find source root dir at %s' % options.src_dir)
+    logging.debug('Overriding source root dir. Using: %s', options.src_dir)
+  else:
+    options.src_dir = \
+        os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
+
+  if not options.landmine_scripts:
+    options.landmine_scripts = [os.path.join(options.src_dir, 'build',
+                                             'get_landmines.py')]
+
   extra_script = os.environ.get('EXTRA_LANDMINES_SCRIPT')
   if extra_script:
-    return options.landmine_scripts + [extra_script]
-  else:
-    return options.landmine_scripts
+    options.landmine_scripts += [extra_script]
+
+  return options
 
 
 def main():
-  landmine_scripts = process_options()
+  options = process_options()
 
   if landmine_utils.builder() in ('dump_dependency_json', 'eclipse'):
     return 0
@@ -123,11 +134,11 @@ def main():
   gyp_environment.SetEnvironment()
 
   landmines = []
-  for s in landmine_scripts:
+  for s in options.landmine_scripts:
     proc = subprocess.Popen([sys.executable, s], stdout=subprocess.PIPE)
     output, _ = proc.communicate()
     landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
-  clobber_if_necessary(landmines)
+  clobber_if_necessary(landmines, options.src_dir)
 
   return 0