Yet more layer tracking logging

 Bug: 17208461

Change-Id: I55e7d0921eb565867e966d68b798b7b92c391b55
diff --git a/libs/hwui/RenderState.h b/libs/hwui/RenderState.h
index 3915fb5..c7ab197 100644
--- a/libs/hwui/RenderState.h
+++ b/libs/hwui/RenderState.h
@@ -29,6 +29,7 @@
 namespace uirenderer {
 
 namespace renderthread {
+class CanvasContext;
 class RenderThread;
 }
 
@@ -57,6 +58,14 @@
         mActiveLayers.erase(layer);
     }
 
+    void registerCanvasContext(renderthread::CanvasContext* context) {
+        mRegisteredContexts.insert(context);
+    }
+
+    void unregisterCanvasContext(renderthread::CanvasContext* context) {
+        mRegisteredContexts.erase(context);
+    }
+
 private:
     friend class renderthread::RenderThread;
     friend class Caches;
@@ -69,6 +78,7 @@
 
     Caches* mCaches;
     std::set<const Layer*> mActiveLayers;
+    std::set<renderthread::CanvasContext*> mRegisteredContexts;
 
     GLsizei mViewportWidth;
     GLsizei mViewportHeight;