android_webview: support building a stub WebView.

android_webview/system_webview_apk_tmpl.gni

 # 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/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/config/locales.gni")
 
 template("system_webview_apk_tmpl") {
   android_apk(target_name) {
     forward_variables_from(invoker, "*")
 
-    deps += [
-      "//android_webview:assets",
-      "//base:base_java",
-    ]
+    if (!defined(webview_stub_only)) {
+      webview_stub_only = false
+    }
+
+    deps += [ "//base:base_java" ]
 
     if (!defined(alternative_android_sdk_jar)) {
       alternative_android_sdk_jar = webview_framework_jar
     }
 
     shared_resources = true
-    shared_libraries = [ "//android_webview:libwebviewchromium" ]
     native_lib_version_rule = "//build/util:chrome_version_json"
     _native_lib_file =
         rebase_path("$root_gen_dir/CHROME_VERSION.json", root_out_dir)
     native_lib_version_arg = "@FileArg($_native_lib_file:full-quoted)"
-    if (build_apk_secondary_abi && android_64bit_target_cpu) {
-      secondary_abi_shared_libraries = [ "//android_webview:libwebviewchromium($android_secondary_abi_toolchain)" ]
+
+    if (webview_stub_only) {
+      unpackaged_shared_libraries = [ "libmonochrome.so" ]
+    } else {
+      deps += [ "//android_webview:assets" ]
+
+      shared_libraries = [ "//android_webview:libwebviewchromium" ]
+      if (build_apk_secondary_abi && android_64bit_target_cpu) {
+        secondary_abi_shared_libraries = [ "//android_webview:libwebviewchromium($android_secondary_abi_toolchain)" ]
+      }
     }
+
     aapt_locale_whitelist = locales
 
     if (!is_java_debug) {
       proguard_enabled = true
       if (!defined(proguard_configs)) {
         proguard_configs = []
       }
       proguard_configs += [
         "//android_webview/apk/java/proguard.flags",
         "//base/android/proguard/chromium_apk.flags",
         "//base/android/proguard/chromium_code.flags",
       ]
     }
   }
 }