gn: Add all v8 targets to gn_all

BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 766 matching lines @@
     deps = [
       "//ipc/mojo:ipc_mojo_perftests",
       "//media/mojo:tests",
       "//media/mojo/services",
       "//mojo:tests",
     ]
   }
 }
 
 group("gn_visibility") {
+  testonly = true

[Michael Achenbach, 2016/06/03 15:17:17]

Not sure about marking this testonly. If I don't I need to put v8:gn_all
somewhere else as  it's testonly.

[Dirk Pranke, 2016/06/03 18:14:54]

Marking this testonly is probably fine.

+
   deps = [
     "//build/config/sanitizers:options_sources",
     # "//third_party/pdfium:pdfium_embeddertests",  # TODO(GYP): visibility?
     # "//third_party/pdfium:pdfium_unittests",  # TODO(GYP): visibility?
   ]
 
   if (!is_ios) {
     deps += [
+      "//v8:gn_all",

[Dirk Pranke, 2016/06/03 18:14:54]

This almost certainly shouldn't be part of "gn_visibility", since the purpose of
this target it to reference only targets that are not otherwise visibile, but
are pulled in by "all".

I think this should probably be a dependency of either ":gn_all", or
":both_gn_and_gyp", or ":gn_only". Ideally it should be one of the latter two,
depending on whether it references targets that exist in both or targets that
exist only in GN. 

If it references a mixture, then it's fine to use gn_all instead.

       "//v8:postmortem-metadata",
       "//v8:v8_snapshot",
     ]
   }
 }
 
 if (!is_ios) {
   # This group includes all of the targets needed to build and test Blink,
   # including running the layout tests (see below).
   group("blink_tests") {
@@ skipping 135 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }