Fixing package-boundary violation with srjar_deps

Without the usage of the srcjar_deps attribute we were not able to
include .java files from other packages without violating the package
boundary contraint.

As an example, in this CL the target "libjingle_peerconnection_java" was
directly including .java files from another packages in its "java_files"
attribute.

Using srcjar_deps we are able to declare the dependency of the target
avoiding to create hidden dependencies in the codebase.

This is not fixing the webrtc:6356 bug directly but it is a first step to
include ThreadUtils classes in libjingle_peerconnection_client_java.jar
again.

It seems also to be related to the chromium:648244 bug. This can be solved
if we can find a way to perform srcjar generation in the android_library
target without changing the semantic of the target.

BUG=webrtc:6356

Review-Url: https://codereview.webrtc.org/2610823002
Cr-Commit-Position: refs/heads/master@{#15914}

webrtc/build/generate_srcjar.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+# TODO(mbonadei): move this script into chromium (build/android/gyp)
+# when approved
+
+import optparse
+import os
+import re
+import sys
+import zipfile
+
+sys.path.insert(0, os.path.abspath(os.path.join(os.pardir, os.pardir, 'build',
+                                                'android', 'gyp', 'util')))
+import build_utils
+
+
+def PackageToPath(src_file):
+  """Returns the path of a .java file according to the package declaration.
+
+  Example:
+  src_file='/home/foo/bar/org/android/TestClass.java'
+  With the following package definition:
+  package org.android;
+
+  It will return 'org/android'.
+
+  Args:
+    A string with the path of the .java source file to analyze.
+
+  Returns:
+    A string with the translation of the package definition into a path.
+  """
+  with open(src_file) as f:
+    file_src = f.read()
+    package = re.search('package (.*);', file_src).group(1)
+    zip_folder = package.replace('.', os.path.sep)
+    file_name = os.path.basename(src_file)
+    return os.path.join(zip_folder, file_name)
+
+
+def DoMain(argv):
+  usage = 'usage: %prog [options] input_file(s)...'
+  parser = optparse.OptionParser(usage=usage)
+  parser.add_option('-s', '--srcjar',
+                    help='The path where the .srcjar file will be generated')
+
+  options, args = parser.parse_args(argv)
+
+  if not args:
+    parser.error('Need to specify at least one input source file (.java)')
+  input_paths = args
+
+  with zipfile.ZipFile(options.srcjar, 'w', zipfile.ZIP_STORED) as srcjar:
+    for src_path in input_paths:
+      zip_path = PackageToPath(src_path)
+      build_utils.AddToZipHermetic(srcjar, zip_path, src_path)
+
+
+if __name__ == '__main__':
+  DoMain(sys.argv[1:])