Set V8 extras mode in gin::V8Initializer.

gin/v8_initializer.cc

Index: gin/v8_initializer.cc
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
index 8bcc78dfa772568d61de2a46bb56e0eaaee95a9d..5440b961c62814f2c9dc42d23ab48845d69e371c 100644
--- a/gin/v8_initializer.cc
+++ b/gin/v8_initializer.cc
@@ -362,17 +362,22 @@ base::PlatformFile V8Initializer::GetOpenSnapshotFileForChildProcesses(
 #endif  // defined(V8_USE_EXTERNAL_STARTUP_DATA)
 
 // static
-void V8Initializer::Initialize(gin::IsolateHolder::ScriptMode mode) {
+void V8Initializer::Initialize(IsolateHolder::ScriptMode mode,
+                               IsolateHolder::V8ExtrasMode v8_extras_mode) {
   static bool v8_is_initialized = false;
   if (v8_is_initialized)
     return;
 
   v8::V8::InitializePlatform(V8Platform::Get());
 
-  if (gin::IsolateHolder::kStrictMode == mode) {
+  if (IsolateHolder::kStrictMode == mode) {
     static const char use_strict[] = "--use_strict";
     v8::V8::SetFlagsFromString(use_strict, sizeof(use_strict) - 1);
   }
+  if (IsolateHolder::kStableAndExperimentalV8Extras == v8_extras_mode) {
+    static const char flag[] = "--experimental_extras";
+    v8::V8::SetFlagsFromString(flag, sizeof(flag) - 1);
+  }
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   v8::StartupData natives;