Oilpan: Enable IncrementalV8FollowupGC behind the HeapIncrementalMarking flag

Schedules an kIncrementalV8FollowupGC instead of an PreciseGC when the HeapIncrementalMarking runtime flag is enabled.

Bug: 757440
Change-Id: I1d05afcc69508592d1e5f411dea1a3afa950baca
Reviewed-on: https://chromium-review.googlesource.com/1095200
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572549}

third_party/blink/renderer/platform/heap/thread_state.cc

@@ -527,9 +527,16 @@ void ThreadState::ScheduleV8FollowupGCIfNeeded(BlinkGC::V8GCType gc_type) {
 
   if ((gc_type == BlinkGC::kV8MajorGC && ShouldForceMemoryPressureGC()) ||
       ShouldScheduleV8FollowupGC()) {
-    VLOG(2) << "[state:" << this << "] "
-            << "ScheduleV8FollowupGCIfNeeded: Scheduled precise GC";
-    SchedulePreciseGC();
+    if (RuntimeEnabledFeatures::HeapIncrementalMarkingEnabled()) {
+      VLOG(2) << "[state:" << this << "] "
+              << "ScheduleV8FollowupGCIfNeeded: Scheduled incremental v8 "
+                 "followup GC";
+      ScheduleIncrementalGC(BlinkGC::GCReason::kIncrementalV8FollowupGC);
+    } else {
+      VLOG(2) << "[state:" << this << "] "
+              << "ScheduleV8FollowupGCIfNeeded: Scheduled precise GC";
+      SchedulePreciseGC();
+    }
     return;
   }
   if (gc_type == BlinkGC::kV8MajorGC && ShouldScheduleIdleGC()) {