Put is_skia_standalone back a bit.

We do still need to know when we're in our GN environment or in another,
like Fuchsia's or Flutter's.

The places where we replaced is_skia_standalone with defined(ndk) still
look right to me as defined(ndk).

CQ_INCLUDE_TRYBOTS=skia.primary:Build-Ubuntu-GCC-x86_64-Release-Flutter_Android

Change-Id: I5455014a8f4a350ac3a939097d042fd8cb4c32fa
Reviewed-on: https://skia-review.googlesource.com/9193
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>

BUILD.gn

@@ -6,6 +6,11 @@
 import("gn/android_framework_defines.gni")
 import("gn/shared_sources.gni")
 
+if (!defined(is_skia_standalone)) {
+  is_skia_standalone = false
+}
+is_skia_dev_build = is_skia_standalone && !is_official_build
+
 declare_args() {
   skia_use_angle = false
   skia_use_expat = true
@@ -25,11 +30,11 @@ declare_args() {
   skia_enable_android_framework_defines = false
   skia_enable_discrete_gpu = true
   skia_enable_effects = true
-  skia_enable_jumper = !is_official_build
+  skia_enable_jumper = is_skia_dev_build
   skia_enable_gpu = true
   skia_enable_pdf = true
-  skia_enable_tools = !is_official_build
-  skia_enable_vulkan_debug_layers = !is_official_build && is_debug
+  skia_enable_tools = is_skia_dev_build
+  skia_enable_vulkan_debug_layers = is_skia_dev_build && is_debug
   skia_vulkan_sdk = getenv("VULKAN_SDK")
 }
 declare_args() {

gn/BUILDCONFIG.gn

@@ -3,6 +3,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+is_skia_standalone = true
+
 # It's best to keep the names and defaults of is_foo flags consistent with Chrome.
 
 declare_args() {