Add incremental_apk_by_default GN arg.

testing/test.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.
 
 # ==============================================================================
 # TEST SETUP
 # ==============================================================================
 
 # Define a test as an executable (or apk on Android) with the "testonly" flag
 # set.
@@ skipping 158 matching lines @@
       } else {
         apk_target = ":$_apk_target"
       }
       test_name = _output_name
       test_type = "gtest"
       test_suite = _output_name
     }
 
     group(target_name) {
       testonly = true
-      deps = [
-        ":$_test_runner_target",
-      ]
-      if (_use_raw_android_executable) {
-        deps += [ ":$_dist_target" ]
+      if (incremental_apk_by_default && !_use_raw_android_executable) {
+        deps = [
+          ":${target_name}_incremental",
+        ]
       } else {
-        deps += [ ":$_apk_target" ]
+        deps = [
+          ":$_test_runner_target",
+        ]
+        if (_use_raw_android_executable) {
+          deps += [ ":$_dist_target" ]
+        } else {
+          deps += [ ":$_apk_target" ]
+        }
       }
     }
 
     # TODO(GYP_GONE): Delete this after we've converted everything to GN.
     # The _run targets exist only for compatibility w/ GYP.
     group("${target_name}_apk_run") {
       testonly = true
       deps = [
         ":${invoker.target_name}",
       ]
@@ skipping 88 matching lines @@
 }
 
 # Test defaults.
 set_defaults("test") {
   if (is_android) {
     configs = default_shared_library_configs
   } else {
     configs = default_executable_configs
   }
 }