Remove unnecessary PagePool locks.

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

Index: third_party/WebKit/Source/platform/heap/PagePool.h
diff --git a/third_party/WebKit/Source/platform/heap/PagePool.h b/third_party/WebKit/Source/platform/heap/PagePool.h
index 7936d6329cca888e7c9c2b3a0a9a499835232b4b..7a3748f6194e2912a22b6b81de8fce6fa24337dd 100644
--- a/third_party/WebKit/Source/platform/heap/PagePool.h
+++ b/third_party/WebKit/Source/platform/heap/PagePool.h
@@ -7,7 +7,6 @@
 
 #include "platform/heap/ThreadState.h"
 #include "wtf/Allocator.h"
-#include "wtf/ThreadingPrimitives.h"
 
 namespace blink {
 
@@ -42,7 +41,6 @@ class PagePool {
   };
 
   PoolEntry* m_pool[BlinkGC::NumberOfArenas];
-  Mutex m_mutex[BlinkGC::NumberOfArenas];
 };
 
 }  // namespace blink