[es6] Define generator prototype as writable prop

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 30c6755b42deda493e429ab90cff06d9f173ff68..7d092b8c0952e08a3a5a57782484ec1ed370288d 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2177,9 +2177,9 @@ bool Genesis::InstallNatives() {
                     Builtins::kIllegal, kUseStrictFunctionMap);
 
     // Create maps for generator functions and their prototypes.  Store those
-    // maps in the native context. Generator functions do not have writable
-    // prototypes, nor do they have "caller" or "arguments" accessors.
-    Handle<Map> strict_function_map(native_context()->strict_function_map());
+    // maps in the native context. Generator functions do not have "caller" or
+    // "arguments" accessors.
+    Handle<Map> strict_function_map(strict_function_map_writable_prototype_);

[caitp (gmail), 2015/05/22 21:11:23]

Can you add a note here about the `{ [[Writable]]: true, [[Enumerable]]: false,
[[Configurable]]: false }.` and point to section 25.2.4.3 (similar to how draft
sections are pointed to in the standard lib sources)

Also note, this is sort of weird, but GeneratorFunction.prototype is
non-writable still (as mentioned in 25.2.2.2

     Handle<Map> sloppy_generator_function_map =
         Map::Copy(strict_function_map, "SloppyGeneratorFunction");
     Map::SetPrototype(sloppy_generator_function_map,