Adds licenses.py support for internal third_party dependencies.

Refactor processing of additional_readme_paths.json into a newly
added ProcessAdditionalReadmePathsJson function

//clank is filtered by default, but projects inside //clank (such as //clank/third_party/elements) might need to
add a license file to about:credits if they depend on open source code.

Bug: 1099355
Change-Id: Id0e03664e1eb2e3b287ed33ee1771f21c13278eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2267919
Commit-Queue: Justin DeWitt <dewittj@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782782}

tools/licenses.py

@@ -113,10 +113,18 @@ PRUNE_DIRS = (VCS_METADATA_DIRS +
 # that contain multiple others as transitive dependencies.
 ADDITIONAL_PATHS_FILENAME = 'additional_readme_paths.json'
 
+# A list of paths that contain license information but that would otherwise
+# not be included.  Possible reasons include:
+#   - Third party directories in //clank which are considered to be Google-owned
+#   - Directories that are directly checked out from upstream, and thus
+#     don't have a README.chromium
+#   - Directories that contain example code, or build tooling.
+#   - Nested third_party code inside other third_party libraries.
 ADDITIONAL_PATHS = (
     os.path.join('chrome', 'common', 'extensions', 'docs', 'examples'),
     os.path.join('chrome', 'test', 'chromeos', 'autotest'),
     os.path.join('chrome', 'test', 'data'),
+    os.path.join('clank', 'third_party', 'elements'),
     os.path.join('native_client'),
     os.path.join('testing', 'gmock'),
     os.path.join('testing', 'gtest'),
@@ -464,6 +472,16 @@ def FilterDirsWithFiles(dirs_list, root):
   return [x for x in dirs_list if ContainsFiles(x, root)]
 
 
+def ProcessAdditionalReadmePathsJson(dirname, third_party_dirs):
+  """For a given directory, process the additional readme paths, and add to
+    third_party_dirs."""
+  additional_paths_file = os.path.join(dirname, ADDITIONAL_PATHS_FILENAME)
+  if os.path.exists(additional_paths_file):
+    with open(additional_paths_file) as paths_file:
+      extra_paths = json.load(paths_file)
+      third_party_dirs.update([os.path.join(dirname, p) for p in extra_paths])
+
+
 def FindThirdPartyDirs(prune_paths, root):
   """Find all third_party directories underneath the source root."""
   third_party_dirs = set()
@@ -485,15 +503,11 @@ def FindThirdPartyDirs(prune_paths, root):
       # Add all subdirectories that are not marked for skipping.
       for dir in dirs:
         dirpath = os.path.join(path, dir)
-        additional_paths_file = os.path.join(root, dirpath,
-                                             ADDITIONAL_PATHS_FILENAME)
         if dirpath not in prune_paths:
           third_party_dirs.add(dirpath)
-        if os.path.exists(additional_paths_file):
-          with open(additional_paths_file) as paths_file:
-            extra_paths = json.load(paths_file)
-            third_party_dirs.update(
-                [os.path.join(dirpath, p) for p in extra_paths])
+
+        additional_paths_dir = os.path.join(root, dirpath)
+        ProcessAdditionalReadmePathsJson(additional_paths_dir, third_party_dirs)
 
       # Don't recurse into any subdirs from here.
       dirs[:] = []
@@ -507,6 +521,8 @@ def FindThirdPartyDirs(prune_paths, root):
   for dir in ADDITIONAL_PATHS:
     if dir not in prune_paths:
       third_party_dirs.add(dir)
+      additional_paths_dir = os.path.join(root, dir)
+      ProcessAdditionalReadmePathsJson(additional_paths_dir, third_party_dirs)
 
   return third_party_dirs