Bug 1546012 - Avoid slow sleeps on Android in TestSPSCQueue; r=padenot

Reducing the sleep to 0 on Android results in a dramatic reduction in run time, and the test
passes consistently.

Differential Revision: https://phabricator.services.mozilla.com/D28296

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

mfbt/tests/TestSPSCQueue.cpp

@@ -80,11 +80,13 @@ void TestRing(int capacity) {
 }
 
 void Delay() {
-  // On Windows, the timer resolution is so bad that, even if we used
-  // `timeBeginPeriod(1)`, any nonzero sleep from the test's inner loops
+  // On Windows and x86 Android, the timer resolution is so bad that, even if
+  // we used `timeBeginPeriod(1)`, any nonzero sleep from the test's inner loops
   // would make this program take far too long.
 #ifdef _WIN32
   Sleep(0);
+#elif defined(ANDROID)
+  std::this_thread::sleep_for(std::chrono::microseconds(0));
 #else
   std::this_thread::sleep_for(std::chrono::microseconds(10));
 #endif