[Cronet] Use gn desc deps to find third_party licenses.

components/cronet/tools/cronet_licenses.py

Index: components/cronet/tools/cronet_licenses.py
diff --git a/components/cronet/tools/cronet_licenses.py b/components/cronet/tools/cronet_licenses.py
index 63a7b07e21d47f79294e7953dd6bbadbff55daf4..160d13928686b02cc43dd60efec79311df51b41f 100755
--- a/components/cronet/tools/cronet_licenses.py
+++ b/components/cronet/tools/cronet_licenses.py
@@ -11,7 +11,10 @@ it depends. Based on android_webview/tools/webview_licenses.py.
 
 import optparse
 import os
+import shutil
+import subprocess
 import sys
+import tempfile
 import textwrap
 
 REPOSITORY_ROOT = os.path.abspath(os.path.join(
@@ -20,6 +23,15 @@ REPOSITORY_ROOT = os.path.abspath(os.path.join(
 sys.path.append(os.path.join(REPOSITORY_ROOT, 'tools'))
 import licenses
 
+third_party_dirs = [
+  'base/third_party/libevent',
+  'third_party/ashmem',
+  'third_party/boringssl',
+  'third_party/modp_b64',
+  'third_party/zlib',
+]
+
+
 def _ReadFile(path):
   """Reads a file from disk.
   Args:
@@ -35,15 +47,6 @@ def GenerateLicense():
   Returns:
     The contents of the LICENSE file.
   """
-  # TODO(mef): Generate list of third_party libraries using checkdeps.
-  third_party_dirs = [
-    'base/third_party/libevent',
-    'third_party/ashmem',
-    'third_party/boringssl',
-    'third_party/modp_b64',
-    'third_party/zlib',
-  ]
-
   # Start with Chromium's LICENSE file
   content = [_ReadFile('LICENSE')]
 
@@ -52,7 +55,7 @@ def GenerateLicense():
     metadata = licenses.ParseDir(directory, REPOSITORY_ROOT,
                                  require_license_file=True)
     content.append('-' * 20)
-    content.append(directory)
+    content.append(directory.split("/")[-1])
     content.append('-' * 20)
     license_file = metadata['License File']
     if license_file and license_file != licenses.NOT_SHIPPED:
@@ -61,6 +64,28 @@ def GenerateLicense():
   return '\n'.join(content)
 
 
+def FindThirdPartyDeps(gn_out_dir):
+  # Generate gn project in temp directory and use it to find dependencies.
+  # Current gn directory cannot ba used because gn doesn't allow recursive
+  # invocations due to potential side effects.
+  try:
+    tmp_dir = tempfile.mkdtemp(dir = gn_out_dir)
+    shutil.copy(gn_out_dir + "/args.gn", tmp_dir)
+    subprocess.check_output(["gn", "gen", tmp_dir])
+    gn_deps = subprocess.check_output(["gn", "desc", tmp_dir, \
+                                    "//net", "deps", "--as=buildfile", "--all"])
+  finally:
+    if os.path.exists(tmp_dir):
+      shutil.rmtree(tmp_dir)
+
+  third_party_deps = []
+  for build_dep in gn_deps.split():
+    if ("third_party" in build_dep and build_dep.endswith("/BUILD.gn")):
+      third_party_deps.append(build_dep.replace("/BUILD.gn", ""))
+  third_party_deps.sort()
+  return third_party_deps
+
+
 def main():
   class FormatterWithNewLines(optparse.IndentedHelpFormatter):
     def format_description(self, description):
@@ -70,11 +95,18 @@ def main():
 
   parser = optparse.OptionParser(formatter=FormatterWithNewLines(),
                                  usage='%prog command [options]')
+  parser.add_option('--gn', help='Use gn deps to find third party dependencies',
+                    action='store_true')
   parser.description = (__doc__ +
                        '\nCommands:\n' \
                        '  license [filename]\n' \
                        '    Generate Cronet LICENSE to filename or stdout.\n')
   (_, args) = parser.parse_args()
+
+  if _.gn:
+    global third_party_dirs
+    third_party_dirs = FindThirdPartyDeps(os.getcwd())
+
   if not args:
     parser.print_help()
     return 1