[Cronet] Add callback wrapper classes to enforce API version checking.

components/cronet/android/BUILD.gn

 # Copyright 2015 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("//build/buildflag_header.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/util/process_version.gni")
 import("//build/util/version.gni")
 import("//testing/test.gni")
@@ skipping 300 matching lines @@
 android_library("cronet_impl_common_java") {
   java_files = [
     "java/src/org/chromium/net/impl/CronetEngineBase.java",
     "java/src/org/chromium/net/impl/CronetEngineBuilderImpl.java",
     "java/src/org/chromium/net/impl/Preconditions.java",
     "java/src/org/chromium/net/impl/RequestFinishedInfoImpl.java",
     "java/src/org/chromium/net/impl/UrlRequestBase.java",
     "java/src/org/chromium/net/impl/UrlRequestBuilderImpl.java",
     "java/src/org/chromium/net/impl/UrlResponseInfoImpl.java",
     "java/src/org/chromium/net/impl/UserAgent.java",
+    "java/src/org/chromium/net/impl/VersionSafeCallbacks.java",
   ]
 
   deps = [
     ":cronet_api_java",
     "//third_party/android_tools:android_support_annotations_java",
   ]
 
   srcjar_deps = cronet_impl_common_java_srcjar_deps
 }
 
@@ skipping 781 matching lines @@
       ":jar_cronet_impl_native_java_source",
       ":jar_cronet_impl_platform_java_source",
       ":jar_cronet_sample_source",
       ":repackage_extracted_jars",
     ]
     if (current_cpu == "arm" && arm_version == 7) {
       deps += [ ":enforce_no_neon" ]
     }
   }
 }