Removed implicit conversion in Folly

Summary: Declared maxReadAtOnce_ in AtomicNotificationQueue.h as uint_32 to avoid implicit conversion in AtomicNotificationQueue-inl.h

Reviewed By: yfeldblum

Differential Revision: D33645415

fbshipit-source-id: 0eb57074951f1320df2dbb1d302cba69a727af56

folly/io/async/AtomicNotificationQueue-inl.h

@@ -321,7 +321,7 @@ bool AtomicNotificationQueue<Task>::drive(Consumer&& consumer) {
     nextQueue = atomicQueue_.getTasks();
   }
   const bool wasAnyProcessed = !queue_.empty() || !nextQueue.empty();
-  for (int32_t numConsumed = 0;
+  for (uint32_t numConsumed = 0;
        maxReadAtOnce_ == 0 || numConsumed < maxReadAtOnce_;) {
     if (queue_.empty()) {
       queue_ = std::move(nextQueue);

folly/io/async/AtomicNotificationQueue.h

@@ -240,7 +240,7 @@ class AtomicNotificationQueue {
   AtomicQueue atomicQueue_;
   Queue queue_;
   std::atomic<ssize_t> taskExecuteCount_{0};
-  int32_t maxReadAtOnce_{10};
+  uint32_t maxReadAtOnce_{10};
 };
 
 /**