Adding option for Proguard jar to be switched.

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")
 
 template("system_webview_apk_tmpl") {
   android_apk(target_name) {
     forward_variables_from(invoker, "*")
 
     deps += [
       "//android_webview:assets",
       "//android_webview:libwebviewchromium",
       "//base:base_java",
     ]
 
     if (!defined(alternative_android_sdk_jar)) {
       alternative_android_sdk_jar = webview_framework_jar
     }
 
     shared_resources = true
     native_libs = [ "libwebviewchromium.so" ]
     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)"
     extensions_to_not_compress = ".lpak,.pak,.bin,.dat"
 
-    if (!is_debug) {
+    if (!is_java_debug) {
       proguard_enabled = true
       proguard_configs = [ "//android_webview/apk/java/proguard.flags" ]
     }
   }
 }