diff --git a/common/mutator.go b/common/mutator.go
new file mode 100644
index 0000000..43721ee
--- /dev/null
+++ b/common/mutator.go
@@ -0,0 +1,69 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package common
+
+import (
+	"android/soong"
+
+	"github.com/google/blueprint"
+)
+
+type AndroidTopDownMutator func(AndroidTopDownMutatorContext)
+
+type AndroidTopDownMutatorContext interface {
+	blueprint.TopDownMutatorContext
+	androidBaseContext
+}
+
+type androidTopDownMutatorContext struct {
+	blueprint.TopDownMutatorContext
+	androidBaseContextImpl
+}
+
+type AndroidBottomUpMutator func(AndroidBottomUpMutatorContext)
+
+type AndroidBottomUpMutatorContext interface {
+	blueprint.BottomUpMutatorContext
+	androidBaseContext
+}
+
+type androidBottomUpMutatorContext struct {
+	blueprint.BottomUpMutatorContext
+	androidBaseContextImpl
+}
+
+func RegisterBottomUpMutator(name string, mutator AndroidBottomUpMutator) {
+	soong.RegisterBottomUpMutator(name, func(ctx blueprint.BottomUpMutatorContext) {
+		if a, ok := ctx.Module().(AndroidModule); ok {
+			actx := &androidBottomUpMutatorContext{
+				BottomUpMutatorContext: ctx,
+				androidBaseContextImpl: a.base().androidBaseContextFactory(ctx),
+			}
+			mutator(actx)
+		}
+	})
+}
+
+func RegisterTopDownMutator(name string, mutator AndroidTopDownMutator) {
+	soong.RegisterTopDownMutator(name, func(ctx blueprint.TopDownMutatorContext) {
+		if a, ok := ctx.Module().(AndroidModule); ok {
+			actx := &androidTopDownMutatorContext{
+				TopDownMutatorContext:  ctx,
+				androidBaseContextImpl: a.base().androidBaseContextFactory(ctx),
+			}
+			mutator(actx)
+		}
+	})
+}