GN: Enable incremental javac by default for debug builds

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) ],
@@ skipping 53 matching lines @@
     findbugs_verbose = false
 
     # Set to true to enable the Errorprone compiler
     use_errorprone_java_compiler = false
 
     # 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
+    enable_incremental_javac = is_debug
 
     # Speed up dexing using dx --incremental.
     enable_incremental_dx = is_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))
 
@@ skipping 137 matching lines @@
   } else if (current_cpu == "x64") {
     android_app_abi = "x86_64"
   } else if (current_cpu == "arm64") {
     android_app_abi = "arm64-v8a"
   } else if (current_cpu == "mips64el") {
     android_app_abi = "mips64"
   } else {
     assert(false, "Unknown Android ABI: " + current_cpu)
   }
 }