Expose gc(true) to JavaScript, which triggers a scavenger GC.

src/extensions/gc-extension.cc

Index: src/extensions/gc-extension.cc
diff --git a/src/extensions/gc-extension.cc b/src/extensions/gc-extension.cc
index f921552aaaa7fa2c3156cb35c5904bfbe1d7f9fc..813b9219bfec7eacd0638cf002c8abb368bba3d2 100644
--- a/src/extensions/gc-extension.cc
+++ b/src/extensions/gc-extension.cc
@@ -40,7 +40,11 @@ v8::Handle<v8::FunctionTemplate> GCExtension::GetNativeFunction(
 
 
 v8::Handle<v8::Value> GCExtension::GC(const v8::Arguments& args) {
-  HEAP->CollectAllGarbage(Heap::kNoGCFlags, "gc extension");
+  if (args[0]->BooleanValue()) {
+    HEAP->CollectGarbage(NEW_SPACE, "gc extension");
+  } else {
+    HEAP->CollectAllGarbage(Heap::kNoGCFlags, "gc extension");
+  }
   return v8::Undefined();
 }