Refactor RenderState and remove unused functionality.

Test: hwui_unit_tests still pass
Change-Id: Ie943671535ab8c5da1bac05985e815e0cb842dc1
diff --git a/libs/hwui/DeferredLayerUpdater.cpp b/libs/hwui/DeferredLayerUpdater.cpp
index 837d546..b772e5b 100644
--- a/libs/hwui/DeferredLayerUpdater.cpp
+++ b/libs/hwui/DeferredLayerUpdater.cpp
@@ -29,12 +29,16 @@
         , mGLContextAttached(false)
         , mUpdateTexImage(false)
         , mLayer(nullptr) {
-    renderState.registerDeferredLayerUpdater(this);
+    renderState.registerContextCallback(this);
 }
 
 DeferredLayerUpdater::~DeferredLayerUpdater() {
     setTransform(nullptr);
-    mRenderState.unregisterDeferredLayerUpdater(this);
+    mRenderState.removeContextCallback(this);
+    destroyLayer();
+}
+
+void DeferredLayerUpdater::onContextDestroyed() {
     destroyLayer();
 }