Use default_args for configuring V8

.gn

 # This file is used by the GN meta build system to find the root of the source
 # tree and to set startup options. For documentation on the values set in this
 # file, run "gn help dotfile" at the command line.
 
 import("//build/dotfile_settings.gni")
 
 # The location of the build configuration file.
 buildconfig = "//build/config/BUILDCONFIG.gn"
 
 # The secondary source root is a parallel directory tree where
 # GN build files are placed when they can not be placed directly
 # in the source tree, e.g. for third party source trees.
 secondary_source = "//build/secondary/"
 
+# These arguments override the default values for items in a declare_args
+# block. "gn args" in turn can override these.
+#
+# In general the value for a build arg in the declare_args block should be the
+# default. In some cases, a DEPS-ed in project will want different defaults for
+# being built as part of Chrome vs. being built standalone. In this case, the
+# Chrome defaults should go here. There should be no overrides here for
+# values declared in the main Chrome repository.
+default_args = {
+  v8_extra_library_files = [
+    # Dependencies used by the extra libraries. Putting them here causes them
+    # to be executed first during snapshot creation.
+    "//third_party/WebKit/Source/core/streams/CommonStrings.js",

[Adam Rice, 2017/01/26 03:59:01]

Is it safe to assume that nothing is going to come along and sort this list?

[Michael Achenbach, 2017/01/26 07:49:21]

good question. Deferring to Brett

+
+    # Extra libraries.
+    "//third_party/WebKit/Source/core/streams/ByteLengthQueuingStrategy.js",
+    "//third_party/WebKit/Source/core/streams/CountQueuingStrategy.js",
+    "//third_party/WebKit/Source/core/streams/ReadableStream.js",
+  ]
+  v8_experimental_extra_library_files =
+      [ "//third_party/WebKit/Source/core/streams/WritableStream.js" ]
+  v8_enable_inspector = true
+  v8_enable_gdbjit = false
+  v8_imminent_deprecation_warnings = false
+}
+
 # These are the targets to check headers for by default. The files in targets
 # matching these patterns (see "gn help label_pattern" for format) will have
 # their includes checked for proper dependencies when you run either
 # "gn check" or "gn gen --check".
 check_targets = [
   #"//apps/*",  # Medium-hard.
   "//ash/*",
   "//base/*",
   "//blink/*",
   "//breakpad/*",
@@ skipping 221 matching lines @@
       "//third_party/google_input_tools/inputview.gni",
 
       # CLD2 should be removed soon, delete this when we do.
       "//third_party/cld_2/BUILD.gn",
       "//tools/grit/grit_rule.gni",
 
       # Not gypi-to-gn.
       "//google_apis/BUILD.gn",
       "//printing/BUILD.gn",
     ]