Introduce a v8::Platform class that bundles embedder callbacks

build/features.gypi

Index: build/features.gypi
diff --git a/build/features.gypi b/build/features.gypi
index 08ea11ae9b972595e5c931bc96e1dc6913e46f5f..85b8a38465cc3203233c1fa809c0a108280f711c 100644
--- a/build/features.gypi
+++ b/build/features.gypi
@@ -58,6 +58,9 @@
 
     # Enable compiler warnings when using V8_DEPRECATED apis.
     'v8_deprecation_warnings%': 0,
+
+    # Use the v8 provided v8::Platform implementation.
+    'v8_use_default_platform%': 1,
   },
   'target_defaults': {
     'conditions': [
@@ -85,6 +88,9 @@
       ['v8_enable_i18n_support==1', {
         'defines': ['V8_I18N_SUPPORT',],
       }],
+      ['v8_use_default_platform==1', {
+        'defines': ['V8_USE_DEFAULT_PLATFORM',],
+      }],
       ['v8_compress_startup_data=="bz2"', {
         'defines': [
           'COMPRESS_STARTUP_DATA_BZ2',