Add initial benchmarks for CanvasOp

Also some minor other tweaks

Test: this
Change-Id: Idb8a5955839893ff000de87d4899fd130ede061c
diff --git a/libs/hwui/Android.bp b/libs/hwui/Android.bp
index 1ff1978..0533aa6 100644
--- a/libs/hwui/Android.bp
+++ b/libs/hwui/Android.bp
@@ -672,6 +672,7 @@
 
     srcs: [
         "tests/microbench/main.cpp",
+        "tests/microbench/CanvasOpBench.cpp",
         "tests/microbench/DisplayListCanvasBench.cpp",
         "tests/microbench/LinearAllocatorBench.cpp",
         "tests/microbench/PathParserBench.cpp",