[gn] Use external startup data by default

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 38ac768786476006948521a1c3943bb126db2f8b..5d178f6452cc4483508954ae0641d83f4d352eb7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -22,6 +22,10 @@ declare_args() {
   # http://v8project.blogspot.com/2015/09/custom-startup-snapshots.html
   v8_use_snapshot = true
 
+  # Use external files for startup data blobs:
+  # the JS builtins sources and the start snapshot.
+  v8_use_external_startup_data = true

[Michael Achenbach, 2016/05/12 08:06:33]

Couldn't find where chromium sets this. Are we maybe not running with external
snapshot at all?

[Michael Achenbach, 2016/05/12 09:24:31]

OK. Found it:
https://code.google.com/p/chromium/codesearch#chromium/src/build_overrides/v8...

But we should still set it to true so that we also use the default in
stand-alone.

[vogelheim, 2016/05/12 12:35:10]

Agreed!

+
   # Sets -DVERIFY_HEAP.
   v8_enable_verify_heap = false