Move //webapk to //chrome/android/webapk

chrome/android/webapk/shell_apk/javatests/canary_lib/BUILD.gn

 # 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("//build/config/android/rules.gni")
 
 android_library("canary_lib") {
   dex_path = "$target_gen_dir/canary.dex"
   java_files = [ "src/org/chromium/webapk/shell_apk/test/canary/Canary.java" ]
 }
 
 android_assets("canary_dex_asset") {
   sources = [
     "$target_gen_dir/canary.dex",
   ]
   disable_compression = true
   deps = [
     ":canary_lib",
   ]
 }