Fix duration in multi-threaded mode.

src/lime/system/ThreadPool.hx

@@ -338,7 +338,7 @@ class ThreadPool extends WorkOutput
 					}
 					while (!Std.isOfType(job, ThreadEvent));
 
-					output.resetJobProgress();
+					output.resetJobProgress(timestamp());
 				}
 
 				if (job.event == EXIT)
@@ -377,7 +377,7 @@ class ThreadPool extends WorkOutput
 				else if(Std.isOfType(interruption, ThreadEvent))
 				{
 					job = interruption;
-					output.resetJobProgress();
+					output.resetJobProgress(timestamp());
 				}
 				else
 				{
@@ -390,7 +390,7 @@ class ThreadPool extends WorkOutput
 	}
 	#end
 
-	private inline function timestamp():Float
+	private static inline function timestamp():Float
 	{
 		#if sys
 		return Sys.cpuTime();

src/lime/system/WorkOutput.hx

@@ -166,9 +166,14 @@ class WorkOutput
 		}
 	}
 
-	private inline function resetJobProgress():Void
+	/**
+		@param now `WorkOutput` won't compile if it includes any references to
+		`haxe.Timer`, so the child class must supply the current time instead.
+	**/
+	private inline function resetJobProgress(now:Float):Void
 	{
 		__jobComplete.value = false;
+		__jobStartTime.value = now;
 		workIterations.value = 0;
 	}