heap: Concurrent marking implies Incremental marking

Concurrent marking relies on incremental marking, so incremental
should be enabled whenever concurrent is enabled.
Current features framework doesn't allow to enable incremental
whenever concurrent is enabled, so instead we check that this
condition is satisfied when we initialize the process heap.

Bug: 986235
Change-Id: I98e464e8f5c6bea700374144dc529e1721cc6f59
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1805650
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702071}

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

@@ -5,6 +5,7 @@
 #include "third_party/blink/renderer/platform/heap/process_heap.h"
 
 #include "base/sampling_heap_profiler/poisson_allocation_sampler.h"
+#include "third_party/blink/public/common/features.h"
 #include "third_party/blink/renderer/platform/heap/gc_info.h"
 #include "third_party/blink/renderer/platform/heap/heap.h"
 #include "third_party/blink/renderer/platform/heap/persistent_node.h"
@@ -27,6 +28,11 @@ void BlinkGCFreeHook(uint8_t* address) {
 }  // namespace
 
 void ProcessHeap::Init() {
+  DCHECK(!base::FeatureList::IsEnabled(
+             blink::features::kBlinkHeapConcurrentMarking) ||
+         base::FeatureList::IsEnabled(
+             blink::features::kBlinkHeapIncrementalMarking));
+
   total_allocated_space_ = 0;
   total_allocated_object_size_ = 0;