Move v8_use_external_startup_data out of //build/config:feature_flags.

ppapi/BUILD.gn

Index: ppapi/BUILD.gn
diff --git a/ppapi/BUILD.gn b/ppapi/BUILD.gn
index fa0d2f1810e60f60ef42757816a5c3211a348410..c9a41ac4d3cd470b1ac50238039c2ea0951e0382 100644
--- a/ppapi/BUILD.gn
+++ b/ppapi/BUILD.gn
@@ -29,6 +29,7 @@ copy("copy_test_files2") {
 
 import("//build/config/features.gni")
 import("//build/config/nacl/config.gni")
+import("//build_overrides/v8.gni")
 import("//ppapi/ppapi_sources.gni")
 import("//testing/test.gni")
 
@@ -47,6 +48,10 @@ shared_library("ppapi_tests") {
     "//ppapi/cpp",
     "//ppapi/shared_impl",
   ]
+
+  if (v8_use_external_startup_data) {
+    configs += [ "//v8:external_startup_data" ]
+  }
 }
 
 shared_library("power_saver_test_plugin") {