[heap] Do not group MinorMC events under GCScavenger trace event name

MinorMC events were incorrectly grouped under the V8.GCScavenger trace event name.

This CL introduces the trace event name V8.GCMinorMC and uses it when MinorMC is used instead of Scavenger.

Change-Id: Ide22526adfa9cc6dec91d3c34186b1c2ea6eb862
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717989
Commit-Queue: Leon Bettscheider <bettscheider@google.com>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81323}

src/heap/gc-tracer.cc

@@ -88,10 +88,15 @@ const char* GCTracer::Event::TypeName(bool short_name) const {
 GCTracer::RecordGCPhasesInfo::RecordGCPhasesInfo(Heap* heap,
                                                  GarbageCollector collector) {
   if (Heap::IsYoungGenerationCollector(collector)) {
-    mode_ = Mode::Scavenger;
     type_timer_ = nullptr;
     type_priority_timer_ = nullptr;
-    trace_event_name_ = "V8.GCScavenger";
+    if (!FLAG_minor_mc) {
+      mode_ = Mode::Scavenger;
+      trace_event_name_ = "V8.GCScavenger";
+    } else {
+      mode_ = Mode::None;
+      trace_event_name_ = "V8.GCMinorMC";
+    }
   } else {
     DCHECK_EQ(GarbageCollector::MARK_COMPACTOR, collector);
     Counters* counters = heap->isolate()->counters();