Verify for_each is const

Test: this
Change-Id: I7ffd755b4b762f7e8608cf84b328560783162439
diff --git a/libs/hwui/tests/unit/CanvasOpTests.cpp b/libs/hwui/tests/unit/CanvasOpTests.cpp
index c90d1a4..84fc6e6 100644
--- a/libs/hwui/tests/unit/CanvasOpTests.cpp
+++ b/libs/hwui/tests/unit/CanvasOpTests.cpp
@@ -138,6 +138,20 @@
     EXPECT_EQ(tracker.alive(), 0);
 }
 
+TEST(CanvasOp, verifyConst) {
+    CanvasOpBuffer buffer;
+    buffer.push<Op::DrawColor>({
+        .color = SkColors::kBlack,
+        .mode = SkBlendMode::kSrcOver,
+    });
+    buffer.for_each([](auto op) {
+        static_assert(std::is_const_v<std::remove_reference_t<decltype(*op)>>,
+                "Expected container to be const");
+        static_assert(std::is_const_v<std::remove_reference_t<decltype(op->op())>>,
+                "Expected op to be const");
+    });
+}
+
 TEST(CanvasOp, simplePush) {
     CanvasOpBuffer buffer;
     EXPECT_EQ(buffer.size(), 0);