Enable heap compaction on all 'container' arenas.

third_party/WebKit/Source/platform/heap/HeapCompact.h

Index: third_party/WebKit/Source/platform/heap/HeapCompact.h
diff --git a/third_party/WebKit/Source/platform/heap/HeapCompact.h b/third_party/WebKit/Source/platform/heap/HeapCompact.h
index 3e6a88375eef214cce2f9f1408b98980787aa759..395f35366ea82d14be8749d490ba24e5f4758d48 100644
--- a/third_party/WebKit/Source/platform/heap/HeapCompact.h
+++ b/third_party/WebKit/Source/platform/heap/HeapCompact.h
@@ -111,6 +111,17 @@ class PLATFORM_EXPORT HeapCompact final {
   // to the new value, returning old.
   static bool ScheduleCompactionGCForTesting(bool);
 
+  // Test-only: verify that one or more of the vector arenas are
+  // in the process of being compacted.
+  bool IsCompactingVectorArenas() {
+    for (int i = BlinkGC::kVector1ArenaIndex; i <= BlinkGC::kVector4ArenaIndex;
+         ++i) {
+      if (IsCompactingArena(i))
+        return true;
+    }
+    return false;
+  }
+
  private:
   class MovableObjectFixups;