TaskRunner starts the background thread only when needed

Test: libhidl_test
Test: hidl_test
Test: boots
Change-Id: I5b6de5cd4a475b0653102e8004953ba008288ab1
diff --git a/base/include/hidl/SynchronizedQueue.h b/base/include/hidl/SynchronizedQueue.h
index 1813130..efb04e0 100644
--- a/base/include/hidl/SynchronizedQueue.h
+++ b/base/include/hidl/SynchronizedQueue.h
@@ -29,6 +29,7 @@
  */
 template <typename T>
 struct SynchronizedQueue {
+    SynchronizedQueue(size_t limit);
 
     /* Gets an item from the front of the queue.
      *
@@ -44,19 +45,18 @@
      */
     size_t size();
 
-    /* Sets the limit to the queue. Will fail
-     * the push operation if the limit is reached.
-     */
-    void setLimit(size_t limit);
-
 private:
     std::condition_variable mCondition;
     std::mutex mMutex;
     std::queue<T> mQueue;
-    size_t mQueueLimit = SIZE_MAX;
+    const size_t mQueueLimit;
 };
 
 template <typename T>
+SynchronizedQueue<T>::SynchronizedQueue(size_t limit) : mQueueLimit(limit) {
+}
+
+template <typename T>
 T SynchronizedQueue<T>::wait_pop() {
     std::unique_lock<std::mutex> lock(mMutex);
 
@@ -94,13 +94,6 @@
     return mQueue.size();
 }
 
-template <typename T>
-void SynchronizedQueue<T>::setLimit(size_t limit) {
-    std::unique_lock<std::mutex> lock(mMutex);
-
-    mQueueLimit = limit;
-}
-
 } // namespace details
 } // namespace hardware
 } // namespace android