Add initial benchmarks for CanvasOp

Also some minor other tweaks

Test: this
Change-Id: Idb8a5955839893ff000de87d4899fd130ede061c
diff --git a/libs/hwui/RenderNode.cpp b/libs/hwui/RenderNode.cpp
index 31e4555..74c70c8 100644
--- a/libs/hwui/RenderNode.cpp
+++ b/libs/hwui/RenderNode.cpp
@@ -380,7 +380,7 @@
     if (mDisplayList) {
         mDisplayList->updateChildren(
                 [&observer, info](RenderNode* child) { child->decParentRefCount(observer, info); });
-        if (!mDisplayList->reuseDisplayList(this, info ? &info->canvasContext : nullptr)) {
+        if (!mDisplayList->reuseDisplayList(this)) {
             delete mDisplayList;
         }
     }