Observatory:

runtime/observatory/lib/src/service/object.dart

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index dcd0afb8e3d9f5a620554a241ca7967a5c93d65e..9bb77fc7895065de98b5c4bfb79a5c24403a3f34 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1380,6 +1380,10 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
     }
   }
 
+  Future collectAllGarbage() {
+    return invokeRpc('_collectAllGarbage', {});
+  }
+
   /// Fetches and builds the class hierarchy for this isolate. Returns the
   /// Object class object.
   Future<Class> getClassHierarchy() {