android: apk_native_libs.py: New Python helper functions.

This CL introduces a new Python script providing various
functions to make it easier to parse Android APK files
for symbolization, i.e.:

- ApkReader: convenience class to read the content of an APK,
  especially information related to uncompressed native shared
  libraries. Mostly useful because it can be easily mocked
  for unit-testing purpose.

- ApkNativeLibrariesMap: convenience class to build a map
  of native shared libraries contained in an APK.

- ApkLibraryPathTranslator: convenience class used to translate
  on-device APK file paths and offsets (as found in stack traces
  or tombstones) into a virtual device library path + offset.

+ Add unit-tests for all features.

+ Add a small apk_lib_dump.py script used to dump the list of
  uncompressed native libraries inside an APK and their file
  start/end offsets and sizes. This is mostly useful for debugging
  symbolization issues.

NOTE: This is a partial rewrite of the corresponding code from
      the following patch, which shows how this will be used in
      the future to better symbolize tombstones:

    https://chromium-review.googlesource.com/c/chromium/src/+/1034054

BUG=755225
R=agrieve@chromium.org, jduborick@chromium.org, pasko@chromium.org, lizeb@chromium.org

Change-Id: If71e0048fa88c859e5f256d8c960134b6b88d06f
Reviewed-on: https://chromium-review.googlesource.com/1047211
Commit-Queue: David Turner <digit@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576193}

build/android/PRESUBMIT.py

@@ -72,6 +72,7 @@ def CommonChecks(input_api, output_api):
           J('pylib', 'output', 'noop_output_manager_test.py'),
           J('pylib', 'output', 'remote_output_manager_test.py'),
           J('pylib', 'results', 'json_results_test.py'),
+          J('pylib', 'symbols', 'apk_native_libs_unittest.py'),
           J('pylib', 'symbols', 'elf_symbolizer_unittest.py'),
           J('pylib', 'utils', 'decorators_test.py'),
           J('pylib', 'utils', 'device_dependencies_test.py'),

build/android/pylib/symbols/apk_lib_dump.py

+#!/usr/bin/env python
+
+# 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.
+
+"""Dump shared library information from an APK file.
+
+This script is used to dump which *uncompressed* native shared libraries an
+APK contains, as well as their position within the file. This is mostly useful
+to diagnose logcat and tombstone symbolization issues when the libraries are
+loaded directly from the APK at runtime.
+
+The default format will print one line per uncompressed shared library with the
+following format:
+
+  0x<start-offset> 0x<end-offset> 0x<file-size> <file-path>
+
+The --format=python option can be used to dump the same information that is
+easy to use in a Python script, e.g. with a line like:
+
+  (0x<start-offset>, 0x<end-offset>, 0x<file-size>, <file-path>),
+"""
+
+import argparse
+import os
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..'))
+
+from pylib.symbols import apk_native_libs
+
+def main():
+  parser = argparse.ArgumentParser(
+      description=__doc__,
+      formatter_class=argparse.RawDescriptionHelpFormatter)
+
+  parser.add_argument('apk', help='Input APK file path.')
+
+  parser.add_argument('--format', help='Select output format',
+                      default='default', choices=['default', 'python'])
+
+  args = parser.parse_args()
+
+  apk_reader = apk_native_libs.ApkReader(args.apk)
+  lib_map = apk_native_libs.ApkNativeLibraries(apk_reader)
+  for lib_path, file_offset, file_size in lib_map.GetDumpList():
+    if args.format == 'python':
+      print '(0x%08x, 0x%08x, 0x%08x, \'%s\'),' % (
+          file_offset, file_offset + file_size, file_size, lib_path)
+    else:
+      print '0x%08x 0x%08x 0x%08x %s' % (
+          file_offset, file_offset + file_size, file_size, lib_path)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())