Represent speed in GCTracer functions as double instead of int.

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index ffc0ced2b0ec075cf386169de628ae763880cd1a..99741170bcb74adb0f2fe0440a21eee358c6e8cd 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -1024,11 +1024,10 @@ double IncrementalMarking::AdvanceIncrementalMarking(
 
   if (step_size_in_bytes == 0) {
     step_size_in_bytes = GCIdleTimeHandler::EstimateMarkingStepSize(
-        static_cast<size_t>(GCIdleTimeHandler::kIncrementalMarkingStepTimeInMs),
-        static_cast<size_t>(
-            heap()
-                ->tracer()
-                ->FinalIncrementalMarkCompactSpeedInBytesPerMillisecond()));
+        GCIdleTimeHandler::kIncrementalMarkingStepTimeInMs,
+        heap()
+            ->tracer()
+            ->FinalIncrementalMarkCompactSpeedInBytesPerMillisecond());
   }
 
   double remaining_time_in_ms = 0.0;