Mojo: Base our epsilon timeouts off of TestTimeouts::tiny_timeout().

mojo/system/test_utils.h

Index: mojo/system/test_utils.h
diff --git a/mojo/system/test_utils.h b/mojo/system/test_utils.h
index 469edaf25833d65af85f1450893d33e58656b15f..c1a1a1e0b47d31d073d92a7d859845f1ba809197 100644
--- a/mojo/system/test_utils.h
+++ b/mojo/system/test_utils.h
@@ -23,6 +23,22 @@ namespace mojo {
 namespace system {
 namespace test {
 
+// Posts the given task (to the given task runner) and waits for it to complete.
+// (Note: Doesn't spin the current thread's message loop, so if you're careless
+// this could easily deadlock.)
+void PostTaskAndWait(scoped_refptr<base::TaskRunner> task_runner,
+                     const tracked_objects::Location& from_here,
+                     const base::Closure& task);
+
+// A timeout smaller than |TestTimeouts::tiny_timeout()|. Warning: This may lead
+// to flakiness, but this is unavoidable if, e.g., you're trying to ensure that
+// functions with timeouts are reasonably accurate. We want this to be as small
+// as possible without causing too much flakiness.
+base::TimeDelta EpsilonTimeout();
+
+// Stopwatch -------------------------------------------------------------------
+
+// A simple "stopwatch" for measuring time elapsed from a given starting point.
 class Stopwatch {
  public:
   Stopwatch() {}
@@ -32,8 +48,8 @@ class Stopwatch {
     start_time_ = base::TimeTicks::HighResNow();
   }
 
-  int64_t Elapsed() {
-    return (base::TimeTicks::HighResNow() - start_time_).InMicroseconds();
+  base::TimeDelta Elapsed() {
+    return base::TimeTicks::HighResNow() - start_time_;
   }
 
  private:
@@ -42,13 +58,6 @@ class Stopwatch {
   DISALLOW_COPY_AND_ASSIGN(Stopwatch);
 };
 
-// Posts the given task (to the given task runner) and waits for it to complete.
-// (Note: Doesn't spin the current thread's message loop, so if you're careless
-// this could easily deadlock.)
-void PostTaskAndWait(scoped_refptr<base::TaskRunner> task_runner,
-                     const tracked_objects::Location& from_here,
-                     const base::Closure& task);
-
 // TestIOThread ----------------------------------------------------------------
 
 class TestIOThread {