[Cronet] add base proguard flags

This CL pulls in base's proguard flags when compiling
cronet_sample_apk and cronet_package.

Cronet will not need to duplicate proguard flags and can
benefit from base proguard file changes.

This saves about 1882 - 1471 = 411 methods from our dex
count for CronetSample.apk and 10kB(4.35%).

BUG=634998

Review-Url: https://codereview.chromium.org/2214013002
Cr-Commit-Position: refs/heads/master@{#417060}

components/cronet/android/BUILD.gn

@@ -402,6 +402,7 @@ android_apk("cronet_sample_apk") {
     proguard_configs = [
       "proguard.cfg",
       "sample/javatests/proguard.cfg",
+      "//base/android/base_proguard_config.flags",
     ]
   }
 }
@@ -717,6 +718,7 @@ android_apk("cronet_perf_test_apk") {
   proguard_configs = [
     "proguard.cfg",
     "test/javaperftests/proguard.cfg",
+    "//base/android/base_proguard_config.flags",
   ]
 }
 
@@ -901,7 +903,6 @@ copy("cronet_package_copy") {
     "$root_out_dir/lib.java/components/cronet/android/cronet_api.jar",
     "//AUTHORS",
     "//chrome/VERSION",
-    "//components/cronet/android/proguard.cfg",
   ]
   outputs = [
     "$_package_dir/{{source_file_part}}",
@@ -912,6 +913,20 @@ copy("cronet_package_copy") {
   ]
 }
 
+action("cronet_combine_proguard_flags") {
+  script = "//components/cronet/tools/generate_proguard_file.py"
+  outputs = [
+    "$_package_dir/proguard.cfg",
+  ]
+
+  args = [
+    "--output-file",
+    rebase_path("$_package_dir/proguard.cfg", root_build_dir),
+    rebase_path("//base/android/base_proguard_config.flags", root_build_dir),
+    rebase_path("//components/cronet/android/proguard.cfg", root_build_dir),
+  ]
+}
+
 copy("cronet_package_copy_native_lib") {
   sources = [
     "$root_out_dir/libcronet.so",
@@ -963,6 +978,7 @@ group("cronet_package") {
   # not including any deps in cronet_package target otherwise.
   if (!(target_cpu == "arm" && arm_version == 7) || !arm_use_neon) {
     deps = [
+      ":cronet_combine_proguard_flags",
       ":cronet_package_copy",
       ":cronet_package_copy_native_lib",
       ":cronet_package_copy_native_lib_unstripped",

components/cronet/android/proguard.cfg

-# Keep annotations used by chromium to keep members referenced by native code
--keep class org.chromium.base.annotations.*Native*
--keep class org.chromium.base.annotations.JNINamespace
--keepclasseswithmembers class org.chromium.** {
-    @org.chromium.base.annotations.AccessedByNative <fields>;
-}
--keepclasseswithmembers class org.chromium.** {
-    @org.chromium.base.annotations.*Native* <methods>;
-}
-
-# TODO(mef) remove unnecessary classes from base, so we don't have to preserve
-# their methods
--keepclasseswithmembers class org.chromium.** {
-    native <methods>;
-}
-
-# TODO(xunjieli): Find an alternative to explictly preserving public classes.
--keep public class org.chromium.net.*
-
 -keep class org.chromium.net.impl.CronetUrlRequest$HeadersList
 -keep class org.chromium.net.impl.ChromiumUrlRequest$ResponseHeadersMap
 
-# Needed so that multiple optimization passes will detect annotations
--keepattributes *Annotation*
-
-# Keep methods used by reflection
--keep class org.chromium.base.annotations.UsedByReflection
--keep @org.chromium.base.annotations.UsedByReflection class *
--keepclassmembers class * {
-    @org.chromium.base.annotations.UsedByReflection *;
-}
-
 # Suppress unnecessary warnings.
 -dontnote org.chromium.net.ProxyChangeListener$ProxyReceiver
 -dontnote org.chromium.net.AndroidKeyStore

components/cronet/android/sample/javatests/proguard.cfg

@@ -3,10 +3,5 @@
     *;
 }
 
-# Test package uses classes from org.chromium.base.
--keep class org.chromium.base.** {
-    @**.VisibleForTesting *;
-}
-
 # TODO(jbudorick): Remove when crbug.com/488192 is fixed.
 -dontwarn org.apache.http.**

components/cronet/tools/generate_proguard_file.py

+#!/usr/bin/env python
+#
+# Copyright 2016 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.
+
+import optparse
+import sys
+
+# Combines files in |input_files| as one proguard file and write that to
+# |output_file|
+def GenerateProguardFile(output_file, input_files):
+  try:
+    with open(output_file, "wb") as target:
+      for input_file in input_files:
+        f = open(input_file, "rb")
+        for line in f:
+          target.write(line)
+  except IOError:
+    raise Exception("Proguard file generation failed")
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option('--output-file',
+          help='Output file for the generated proguard file')
+
+  options, input_files = parser.parse_args()
+  GenerateProguardFile(options.output_file, input_files)
+
+
+if __name__ == '__main__':
+  sys.exit(main())