GN: add a flag to implement Android_FrameworkDefs bot.

BUILD.gn

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("gn/shared_sources.gni")
 
 declare_args() {
   skia_enable_tools = !is_fuchsia && !is_component_build
 
   skia_use_expat = true
   skia_use_fontconfig = is_linux
   skia_use_freetype = is_android || is_fuchsia || is_linux
   skia_use_giflib = !is_fuchsia
   skia_use_libjpeg_turbo = true
   skia_use_libpng = true
   skia_use_libwebp = !is_fuchsia
   skia_use_sfntly = !is_fuchsia
   skia_use_vulkan = false
   skia_use_zlib = true
+
+  skia_enable_android_framework_defines = false
 }
 
 fontmgr_android_enabled = skia_use_expat && skia_use_freetype
 
 skia_public_includes = [
   "include/android",
   "include/c",
   "include/codec",
   "include/config",
   "include/core",
@@ skipping 184 matching lines @@
                                "sources_when_disabled",
                              ])
       if (defined(invoker.sources_when_disabled)) {
         sources = invoker.sources_when_disabled
       }
       configs += skia_library_configs
     }
   }
 }
 
+optional("android_framework_defines") {
+  enabled = skia_enable_android_framework_defines
+  public_defines = skia_android_framework_defines
+}
+
 optional("fontmgr_android") {
   enabled = fontmgr_android_enabled
 
   deps = [
     "//third_party/expat",
     "//third_party/freetype2",
   ]
   sources = [
     "src/ports/SkFontMgr_android.cpp",
     "src/ports/SkFontMgr_android_factory.cpp",
@@ skipping 142 matching lines @@
     "src/xml/SkXMLParser.cpp",
     "src/xml/SkXMLWriter.cpp",
   ]
 }
 
 component("skia") {
   public_configs = [ ":skia_public" ]
   configs += skia_library_configs
 
   deps = [
+    ":android_framework_defines",
     ":arm64",
     ":armv7",
     ":avx",
     ":crc32",
     ":dsp",
     ":fontmgr_android",
     ":fontmgr_custom",
     ":fontmgr_fontconfig",
     ":fontmgr_fuchsia",
     ":gif",
@@ skipping 442 matching lines @@
     sources = [
       "tools/SkShaper_primitive.cpp",
       "tools/using_skia_and_harfbuzz.cpp",
     ]
     deps = [
       ":skia",
     ]
     testonly = true
   }
 }