Recycle OffscreenBuffers

Change-Id: Ia2e219026f211a5308ecf8209c5f986bb888aadd
diff --git a/libs/hwui/renderstate/RenderState.cpp b/libs/hwui/renderstate/RenderState.cpp
index 9637117..4fa8200 100644
--- a/libs/hwui/renderstate/RenderState.cpp
+++ b/libs/hwui/renderstate/RenderState.cpp
@@ -90,6 +90,8 @@
     }
 */
 
+    mLayerPool.clear();
+
     // TODO: reset all cached state in state objects
     std::for_each(mActiveLayers.begin(), mActiveLayers.end(), layerLostGlContext);
     mAssetAtlas.terminate();
@@ -106,6 +108,19 @@
     mStencil = nullptr;
 }
 
+void RenderState::flush(Caches::FlushMode mode) {
+    switch (mode) {
+        case Caches::FlushMode::Full:
+            // fall through
+        case Caches::FlushMode::Moderate:
+            // fall through
+        case Caches::FlushMode::Layers:
+            mLayerPool.clear();
+            break;
+    }
+    mCaches->flush(mode);
+}
+
 void RenderState::setViewport(GLsizei width, GLsizei height) {
     mViewportWidth = width;
     mViewportHeight = height;