Bug 1604585 - Remove HashTable::mEntered, as it is write-only. r=froydnj

And while at it, initialize mMutationCount in the declaration, to remove an
ugly ifdef block.

Differential Revision: https://phabricator.services.mozilla.com/D57506

--HG--
extra : moz-landing-system : lando

mfbt/HashTable.h

@@ -1527,7 +1527,6 @@ class HashTable : private AllocPolicy {
     mRemovedCount = aRhs.mRemovedCount;
 #ifdef DEBUG
     mMutationCount = aRhs.mMutationCount;
-    mEntered = aRhs.mEntered;
 #endif
     aRhs.mTable = nullptr;
     aRhs.clearAndCompact();
@@ -1547,8 +1546,7 @@ class HashTable : private AllocPolicy {
   uint32_t mRemovedCount;   // removed entry sentinels in mTable
 
 #ifdef DEBUG
-  uint64_t mMutationCount;
-  mutable bool mEntered;
+  uint64_t mMutationCount = 0;
 #endif
 
   // The default initial capacity is 32 (enough to hold 16 elements), but it
@@ -1669,11 +1667,6 @@ class HashTable : private AllocPolicy {
         mTable(nullptr),
         mEntryCount(0),
         mRemovedCount(0)
-#ifdef DEBUG
-        ,
-        mMutationCount(0),
-        mEntered(false)
-#endif
   {
   }