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

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 5d9e588933e47cbab845f1cfec3cfb3e6ce30ee8..dc4c2c6d822d64189e4f5cd4e61405a25ab412cd 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -5,6 +5,7 @@
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
+import("//build_overrides/v8.gni")
 import("//content/browser/browser.gni")
 import("//media/media_options.gni")
 
@@ -136,6 +137,10 @@ source_set("browser") {
       "//ui/surface",
       "//ui/touch_selection",
     ]
+
+    if (v8_use_external_startup_data) {
+      configs += [ "//v8:external_startup_data" ]
+    }
   }
 
   configs += [