Bug 1481998 - Define lookup() in terms of readonlyThreadsafeLookup(). r=luke

The two functions are almost identical. This change minimizes duplication.

--HG--
extra : rebase_source : 08bb79d21084eec63702525ce6179e22686bec5c

mfbt/HashTable.h

@@ -2112,16 +2112,6 @@ public:
     return aMallocSizeOf(this) + shallowSizeOfExcludingThis(aMallocSizeOf);
   }
 
-  MOZ_ALWAYS_INLINE Ptr lookup(const Lookup& aLookup) const
-  {
-    ReentrancyGuard g(*this);
-    if (!HasHash<HashPolicy>(aLookup)) {
-      return Ptr();
-    }
-    HashNumber keyHash = prepareHash(aLookup);
-    return Ptr(lookup<ForNonAdd>(aLookup, keyHash), *this);
-  }
-
   MOZ_ALWAYS_INLINE Ptr readonlyThreadsafeLookup(const Lookup& aLookup) const
   {
     if (!HasHash<HashPolicy>(aLookup)) {
@@ -2131,6 +2121,12 @@ public:
     return Ptr(lookup<ForNonAdd>(aLookup, keyHash), *this);
   }
 
+  MOZ_ALWAYS_INLINE Ptr lookup(const Lookup& aLookup) const
+  {
+    ReentrancyGuard g(*this);
+    return readonlyThreadsafeLookup(aLookup);
+  }
+
   MOZ_ALWAYS_INLINE AddPtr lookupForAdd(const Lookup& aLookup) const
   {
     ReentrancyGuard g(*this);