heap: Fix V8.GCMainThreadMarkingThroughput

Some scopes that were subtracted were not part of the outer scopes and
thus can result in negative values.

Change-Id: I2264b27c4b7a48075fed4e3afaa6b6dd27d8daa4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1762299Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63298}

src/heap/gc-tracer.cc

@@ -1203,10 +1203,7 @@ void GCTracer::RecordGCPhasesHistograms(TimedHistogram* gc_timer) {
       DCHECK_GT(overall_marking_time, 0.0);
       const double overall_v8_marking_time =
           overall_marking_time -
-          current_.scopes[Scope::MC_MARK_EMBEDDER_PROLOGUE] -
-          current_.scopes[Scope::MC_MARK_EMBEDDER_TRACING] -
-          current_.scopes[Scope::MC_INCREMENTAL_EMBEDDER_PROLOGUE] -
-          current_.scopes[Scope::MC_INCREMENTAL_EMBEDDER_TRACING];
+          current_.scopes[Scope::MC_MARK_EMBEDDER_TRACING];
       DCHECK_GT(overall_v8_marking_time, 0.0);
       const int main_thread_marking_throughput_mb_per_s =
           static_cast<int>(static_cast<double>(heap_->SizeOfObjects()) /