Make all GCs from memory reducer incremental.

src/heap/memory-reducer.cc

Index: src/heap/memory-reducer.cc
diff --git a/src/heap/memory-reducer.cc b/src/heap/memory-reducer.cc
index 33e624978ffc21bfc584cace7a2bdbbd62302c84..ee1009134bc75ec9c9ed721ecc3ad0770a34a1d5 100644
--- a/src/heap/memory-reducer.cc
+++ b/src/heap/memory-reducer.cc
@@ -73,14 +73,7 @@ void MemoryReducer::NotifyTimer(const Event& event) {
       PrintIsolate(heap()->isolate(), "Memory reducer: started GC #%d\n",
                    state_.started_gcs);
     }
-    if (heap()->ShouldOptimizeForMemoryUsage()) {
-      // TODO(ulan): Remove this once crbug.com/552305 is fixed.
-      // Do full GC if memory usage has higher priority than latency.
-      heap()->CollectAllGarbage(Heap::kReduceMemoryFootprintMask,
-                                "memory reducer");
-    } else {
-      heap()->StartIdleIncrementalMarking();
-    }
+    heap()->StartIdleIncrementalMarking();
   } else if (state_.action == kWait) {
     if (!heap()->incremental_marking()->IsStopped() &&
         heap()->ShouldOptimizeForMemoryUsage()) {