Add incremental_apk_by_default GN arg.

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) {
   import("//build_overrides/build.gni")
 
   has_chrome_android_internal =
@@ skipping 128 matching lines @@
     # functions are called at startup.
     use_order_profiling = false
 
     # Builds secondary abi for APKs, supports build 32-bit arch as secondary
     # abi in 64-bit Monochrome and WebView.
     build_apk_secondary_abi = true
 
     # Enables java8 language features (via retrolambda).
     # work-in-progress (http://crbug.com/642600)
     use_java8 = false
+
+    # Build incremental targets whenever possible.
+    # Ex. with this arg set to true, the chrome_public_apk target result in
+    # chrome_public_apk_incremental being built.
+    incremental_apk_by_default = false
   }
 
   # We need a second declare_args block to make sure we are using the overridden
   # value of the arguments set above.
   declare_args() {
     # Speed up dexing using dx --incremental.
     enable_incremental_dx = is_java_debug
   }
 
   # Neither of these should ever be used for release builds since they are
@@ skipping 181 matching lines @@
           "//build/toolchain/android:android_${android_secondary_abi_cpu}"
     }
   }
 }
 
 declare_args() {
   # Enables used resource whitelist generation. Set for official builds only
   # as a large amount of build output is generated.
   enable_resource_whitelist_generation = is_android && is_official_build
 }