Update from chromium https://crrev.com/302282

build/config/android/config.gni

 # 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.
 
 # This file contains common system config stuff for the Android build.
 
 if (is_android) {
   has_chrome_android_internal = exec_script("//build/dir_exists.py",
           [ rebase_path("//clank", root_build_dir) ],
           "string") == "True"
 
   if (has_chrome_android_internal) {
     import("//clank/config.gni")
   } else {
     default_android_sdk_root = "//third_party/android_tools/sdk"
     default_android_sdk_version = "21"
     default_android_sdk_build_tools_version = "21.0.1"
   }
 
   declare_args() {
-    # Absolute directory containing the Android source code.
-    android_src = ""
-
     android_sdk_root = default_android_sdk_root
     android_sdk_version = default_android_sdk_version
     android_sdk_build_tools_version = default_android_sdk_build_tools_version
 
     # This is set when building the Android WebView inside the Android build
     # system, using the 'android' gyp backend. The WebView code is still built
     # when this is unset, but builds using the normal chromium build system.
     is_android_webview_build = false
 
     android_default_keystore_path = "//build/android/ant/chromium-debug.keystore"
     android_default_keystore_name = "chromiumdebugkey"
     android_default_keystore_password = "chromium"
 
     # This is a unique identifier for a given build. It's used for
     # identifying various build artifacts corresponding to a particular build of
     # chrome (e.g. where to find archived symbols).
     android_chrome_build_id = "\"\""
   }
 
-  if (is_android_webview_build) {
-    assert(android_src != "",
-           "You must specify android_src for an Android WebView build.")
-  }
-
   # Host stuff -----------------------------------------------------------------
 
   # Defines the name the Android build gives to the current host CPU
   # architecture, which is different than the names GN uses.
   if (build_cpu_arch == "x64") {
     android_host_arch = "x86_64"
   } else if (build_cpu_arch == "x86") {
     android_host_arch = "x86"
   } else {
     assert(false, "Need Android toolchain support for your build CPU arch.")
@@ skipping 95 matching lines @@
   } else if (cpu_arch == "mipsel") {
     android_app_abi = "mips"
   } else {
     assert(false, "Unknown Android ABI: " + cpu_arch)
   }
 } else {
   if (!defined(is_android_webview_build)) {
     is_android_webview_build = false
   }
 }