Adding option for Proguard jar to be switched.

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) {
   assert(rebase_path("//", root_build_dir) == "../../",
          "Android output directory must be nested 2 levels within src/ (" +
              "e.g.: out-gn/Debug). http://crbug.com/412935")
@@ skipping 78 matching lines @@
     # Set to true to run findbugs on JAR targets.
     run_findbugs = false
 
     # Set to true to enable verbose findbugs logging. This does nothing if
     # run_findbugs is false.
     findbugs_verbose = false
 
     # Enables verbose proguard output (summaries and unfiltered output).
     proguard_verbose = false
 
+    # Java debug on Android. Having this on enables multidexing, and turning it
+    # off will enable proguard. To access this flag from within Java code, look
+    # at BuildConfig.IS_DEBUG, which is wired to this arg.
+    is_java_debug = is_debug
+
     # Set to true to enable the Errorprone compiler
     use_errorprone_java_compiler = false
 
     # Enables EMMA Java code coverage. Instruments classes during build to
     # produce .ec files during runtime
     emma_coverage = false
 
     # EMMA filter string consisting of a list of inclusion/exclusion patterns
     # separated with whitespace and/or comma. Only has effect if
     # emma_coverage==true
     emma_filter = ""
 
     # Disables process isolation when building _incremental targets.
     # Required for Android M+ due to SELinux policies (stronger sandboxing).
     disable_incremental_isolated_processes = false
 
     # Speed up incremental compiles by compiling only changed files.
     enable_incremental_javac = false
 
     # Speed up dexing using dx --incremental.
-    enable_incremental_dx = is_debug
+    enable_incremental_dx = is_java_debug
 
     # Neither of these should ever be used for release builds since they are
     # somewhat experimental and dx --incremental is known to not produce
     # byte-for-byte identical output.
     assert(!(enable_incremental_dx && !is_debug))
     assert(!(enable_incremental_javac && !is_debug))
 
     # Adds intrumentation to each function. Writes a file with the order that
     # functions are called at startup.
     use_order_profiling = false
@@ skipping 140 matching lines @@
   } else if (current_cpu == "mips64el") {
     android_app_abi = "mips64"
   } else {
     assert(false, "Unknown Android ABI: " + current_cpu)
   }
 
   if (android_libcpp_lib_dir == "") {
     android_libcpp_lib_dir = "${android_libcpp_root}/libs/${android_app_abi}"
   }
 }