Support external startup data in V8. (retry)

build/features.gypi

Index: build/features.gypi
diff --git a/build/features.gypi b/build/features.gypi
index 5d53c9521e1fab068027a32b7967691042670a58..e808788657f2bf967bbf1fde209cf604c4295fc0 100644
--- a/build/features.gypi
+++ b/build/features.gypi
@@ -61,6 +61,10 @@
 
     # Use the v8 provided v8::Platform implementation.
     'v8_use_default_platform%': 1,
+
+    # Use external files for startup data blobs:
+    # the JS builtins sources and the start snapshot.
+    'v8_use_external_startup_data%': 0,
   },
   'target_defaults': {
     'conditions': [
@@ -92,9 +96,10 @@
         'defines': ['V8_USE_DEFAULT_PLATFORM',],
       }],
       ['v8_compress_startup_data=="bz2"', {
-        'defines': [
-          'COMPRESS_STARTUP_DATA_BZ2',
-        ],
+        'defines': ['COMPRESS_STARTUP_DATA_BZ2',],
+      }],
+      ['v8_use_external_startup_data==1', {
+        'defines': ['V8_USE_EXTERNAL_STARTUP_DATA',],
       }],
     ],  # conditions
     'configurations': {