AW: presubmit check for annotated InvocationHandlers in support lib

This adds a presubmit check in the support library that all references
to InvocationHandlers should be annotated with the type they represent.

Annotations take the form of comments:

/* RetType */ InvocationHandler m(/* ParamType */ InvocationHandler p);

This intentionally skips import statements. The presubmit check is only
a warning, in case of false-positive.

Bug: 842022
Test: git cl presubmit -f --upload
Change-Id: I298d488d14f4fe828b02f4ac062bba6d4b1e9ae8
Reviewed-on: https://chromium-review.googlesource.com/1059009Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558817}

android_webview/support_library/PRESUBMIT.py

+# Copyright 2018 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.
+"""Presubmit tests for android_webview/support_library/
+
+Runs various style checks before upload.
+"""
+
+def CheckChangeOnUpload(input_api, output_api):
+  results = []
+  results.extend(_CheckAnnotatedInvocationHandlers(input_api, output_api))
+  return results
+
+def _CheckAnnotatedInvocationHandlers(input_api, output_api):
+  """Checks that all references to InvocationHandlers are annotated with a
+  comment describing the class the InvocationHandler represents. This does not
+  check .../support_lib_boundary/util/, because this has legitimate reasons to
+  refer to InvocationHandlers without them standing for a specific type.
+  """
+
+  invocation_handler_str = r'\bInvocationHandler\b'
+  annotation_str = r'/\* \w+ \*/\s+'
+  invocation_handler_import_pattern = input_api.re.compile(
+      r'^import.*' + invocation_handler_str + ';$')
+  possibly_annotated_handler_pattern = input_api.re.compile(
+      r'(' + annotation_str + r')?(' + invocation_handler_str + r')')
+
+  errors = []
+
+  sources = lambda affected_file: input_api.FilterSourceFile(
+      affected_file,
+      black_list=(input_api.DEFAULT_BLACK_LIST +
+                  (r'.*support_lib_boundary[\\\/]util[\\\/].*',)),
+      white_list=(r'.*\.java$',))
+
+  for f in input_api.AffectedSourceFiles(sources):
+    for line_num, line in f.ChangedContents():
+      if not invocation_handler_import_pattern.search(line):
+        for match in possibly_annotated_handler_pattern.findall(line):
+          annotation = match[0]
+          if not annotation:
+            # Note: we intentionally double-count lines which have multiple
+            # mistakes, since we require each mention of 'InvocationHandler' to
+            # be annotated.
+            errors.append("%s:%d" % (f.LocalPath(), line_num))
+
+  results = []
+
+  if errors:
+    results.append(output_api.PresubmitPromptWarning("""
+All references to InvocationHandlers should be annotated with the type they
+represent using a comment, e.g.:
+
+/* RetType */ InvocationHandler method(/* ParamType */ InvocationHandler param);
+""",
+        errors))
+
+  return results