Make javac invocations incremental when possible

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 51 matching lines @@
     # Set to true to enable verbose findbugs logging. This does nothing if
     # run_findbugs is false.
     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.
+    incremental_javac = false
   }
 
   # Host stuff -----------------------------------------------------------------
 
   # Defines the name the Android build gives to the current host CPU
   # architecture, which is different than the names GN uses.
   if (host_cpu == "x64") {
     android_host_arch = "x86_64"
   } else if (host_cpu == "x86") {
     android_host_arch = "x86"
@@ skipping 129 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)
   }
 }