[tracing] Support ConvertableToTraceFormat argument type.

test/cctest/libplatform/test-tracing.cc

Index: test/cctest/libplatform/test-tracing.cc
diff --git a/test/cctest/libplatform/test-tracing.cc b/test/cctest/libplatform/test-tracing.cc
index 2e15d6af9e0e356f256b00eb0784fb248db196d3..069316d73f816c7870683cef42ffeb1636d60ce8 100644
--- a/test/cctest/libplatform/test-tracing.cc
+++ b/test/cctest/libplatform/test-tracing.cc
@@ -44,6 +44,18 @@ TEST(TestTraceObject) {
   CHECK_EQ(0, trace_object.cpu_duration());
 }
 
+class ConvertableToTraceFormatMock : public v8::ConvertableToTraceFormat {
+ public:
+  explicit ConvertableToTraceFormatMock(int value) : value_(value) {}
+
+  void AppendAsTraceFormat(std::string* out) const override {
+    *out += "[" + std::to_string(value_) + "," + std::to_string(value_) + "]";
+  }
+
+ private:
+  int value_;
+};
+
 class MockTraceWriter : public TraceWriter {
  public:
   void AppendTraceEvent(TraceObject* trace_event) override {
@@ -264,6 +276,12 @@ TEST(TestTracingControllerMultipleArgsAndCopy) {
     mm = "CHANGED";
     mmm = "CHANGED";
 
+    TRACE_EVENT_INSTANT1("v8", "v8.Test", TRACE_EVENT_SCOPE_THREAD, "a1",
+                         new ConvertableToTraceFormatMock(42));
+    TRACE_EVENT_INSTANT2("v8", "v8.Test", TRACE_EVENT_SCOPE_THREAD, "a1",
+                         new ConvertableToTraceFormatMock(42), "a2",
+                         new ConvertableToTraceFormatMock(123));
+
     tracing_controller.StopTracing();
   }
 
@@ -274,7 +292,7 @@ TEST(TestTracingControllerMultipleArgsAndCopy) {
   GetJSONStrings(all_names, trace_str, "\"name\"", "\"", "\"");
   GetJSONStrings(all_cats, trace_str, "\"cat\"", "\"", "\"");
 
-  CHECK_EQ(all_args.size(), 22);
+  CHECK_EQ(all_args.size(), 24);
   CHECK_EQ(all_args[0], "\"aa\":11");
   CHECK_EQ(all_args[1], "\"bb\":22");
   CHECK_EQ(all_args[2], "\"cc\":33");
@@ -303,6 +321,8 @@ TEST(TestTracingControllerMultipleArgsAndCopy) {
   CHECK_EQ(all_names[20], "INIT");
   CHECK_EQ(all_names[21], "INIT");
   CHECK_EQ(all_args[21], "\"mm1\":\"INIT\",\"mm2\":\"\\\"INIT\\\"\"");
+  CHECK_EQ(all_args[22], "\"a1\":[42,42]");
+  CHECK_EQ(all_args[23], "\"a1\":[42,42],\"a2\":[123,123]");
 
   i::V8::SetPlatformForTesting(old_platform);
 }