Decouple future and fiber for mobile

Summary:
folly::fibers have a bunch of dependencies that are shaky on mobiles.
Decoupling it by using folly::Baton instead of folly::fibers::Baton. Should have
zero effect on fbcode cases.

Reviewed By: djwatson, yfeldblum

Differential Revision: D2821603

fb-gh-sync-id: 0ce3472c9eedf97224e8584d25e04515396cd18e

folly/Baton.h

@@ -217,6 +217,13 @@ struct Baton {
     }
   }
 
+  /// Similar to timed_wait, but with a duration.
+  template <typename Clock = std::chrono::steady_clock, typename Duration>
+  bool timed_wait(const Duration& duration) {
+    auto deadline = Clock::now() + duration;
+    return timed_wait(deadline);
+  }
+
   /// Similar to wait, but doesn't block the thread if it hasn't been posted.
   ///
   /// try_wait has the following semantics:

folly/futures/Future-inl.h

@@ -21,17 +21,32 @@
 #include <chrono>
 #include <random>
 #include <thread>
-#include <folly/experimental/fibers/Baton.h>
+#include <folly/Baton.h>
 #include <folly/Optional.h>
 #include <folly/Random.h>
 #include <folly/Traits.h>
 #include <folly/futures/detail/Core.h>
 #include <folly/futures/Timekeeper.h>
 
+#if defined(__ANDROID__) || defined(__APPLE__)
+#define FOLLY_FUTURE_USING_FIBER 0
+#else
+#define FOLLY_FUTURE_USING_FIBER 1
+#include <folly/experimental/fibers/Baton.h>
+#endif
+
 namespace folly {
 
 class Timekeeper;
 
+namespace detail {
+#if FOLLY_FUTURE_USING_FIBER
+typedef folly::fibers::Baton FutureBatonType;
+#else
+typedef folly::Baton<> FutureBatonType;
+#endif
+}
+
 namespace detail {
   std::shared_ptr<Timekeeper> getTimekeeperSingleton();
 }
@@ -937,7 +952,7 @@ void waitImpl(Future<T>& f) {
   // short-circuit if there's nothing to do
   if (f.isReady()) return;
 
-  folly::fibers::Baton baton;
+  FutureBatonType baton;
   f.setCallback_([&](const Try<T>& t) { baton.post(); });
   baton.wait();
   assert(f.isReady());
@@ -950,7 +965,7 @@ void waitImpl(Future<T>& f, Duration dur) {
 
   folly::MoveWrapper<Promise<T>> promise;
   auto ret = promise->getFuture();
-  auto baton = std::make_shared<folly::fibers::Baton>();
+  auto baton = std::make_shared<FutureBatonType>();
   f.setCallback_([baton, promise](Try<T>&& t) mutable {
     promise->setTry(std::move(t));
     baton->post();

folly/futures/test/TimesTest.cpp

@@ -16,6 +16,7 @@
 
 #include <memory>
 #include <mutex>
+#include <queue>
 
 #include <gtest/gtest.h>
 #include <glog/logging.h>

folly/futures/test/WaitTest.cpp

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#include <queue>
+
 #include <gtest/gtest.h>
 
 #include <folly/futures/Future.h>

folly/futures/test/WhileDoTest.cpp

@@ -16,6 +16,7 @@
 
 #include <memory>
 #include <mutex>
+#include <queue>
 
 #include <gtest/gtest.h>
 #include <glog/logging.h>