Use proguard.cfg in cronet sample apk.

components/cronet.gypi

 # Copyright 2014 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.
 
 {
   'conditions': [
     ['OS=="android" and use_icu_alternatives_on_android==1', {
       # TODO(mef): Figure out what needs to be done for gn script.
       'targets': [
         {
@@ skipping 313 matching lines @@
                 '<(SHARED_LIB_DIR)/<(native_lib)',
               ],
             },
           ],
         },
         {
           'target_name': 'cronet_sample_apk',
           'type': 'none',
           'dependencies': [
             'cronet',
+            'cronet_stub',
           ],
           'variables': {
             'apk_name': 'CronetSample',
             'java_in_dir': 'cronet/android/sample',
             'resource_dir': 'cronet/android/sample/res',
             'native_lib_target': 'libcronet',
+            'proguard_enabled': 'true',
+            'proguard_flags_paths': [
+              'cronet/android/proguard.cfg',
+              # Proguard config for instrumentation test apk.
+              'cronet/android/sample/javatests/proguard.cfg',
+            ],
           },
           'includes': [ '../build/java_apk.gypi' ],
         },
         {
           # cronet_sample_apk creates a .jar as a side effect. Any java targets
           # that need that .jar in their classpath should depend on this target,
           # cronet_sample_apk_java. Dependents of cronet_sample_apk receive its
           # jar path in the variable 'apk_output_jar_path'. This target should
           # only be used by targets which instrument cronet_sample_apk.
           'target_name': 'cronet_sample_apk_java',
           'type': 'none',
           'dependencies': [
             'cronet_sample_apk',
           ],
           'includes': [ '../build/apk_fake_jar.gypi' ],
         },
         {
           'target_name': 'cronet_sample_test_apk',
           'type': 'none',
           'dependencies': [
+            'cronet',
             'cronet_sample_apk_java',
+            'cronet_stub',
             '../base/base.gyp:base_java',
             '../base/base.gyp:base_javatests',
             '../base/base.gyp:base_java_test_support',
             # TODO(mef): Figure out why some tests are failing.
             #'../net/net.gyp:net_javatests',
             #'../net/net.gyp:net_java_test_support',
           ],
           'variables': {
             'apk_name': 'CronetSampleTest',
             'java_in_dir': 'cronet/android/sample/javatests',
+            'proguard_enabled': 'true',
             'resource_dir': 'cronet/android/sample/res',
             'is_test_apk': 1,
           },
           'includes': [ '../build/java_apk.gypi' ],
         },
       ],
     }],  # OS=="android"
   ],
 }