rename limiter to throttle and refactor

- don't inject raf/setTimeout since we can't really mock them w/ a good degree of timing accuracy anyways

fix some unrelated tests

api/tests/test-throttle.js

@@ -0,0 +1,84 @@
+"use strict"
+
+var o = require("../../ospec/ospec")
+var callAsync = require("../../test-utils/callAsync")
+var throttle = require("../../api/throttle")
+
+o.spec("throttle", function() {
+	var FRAME_BUDGET = 1000 / 60
+	var spy, throttled
+	o.beforeEach(function() {
+		spy = o.spy()
+		throttled = throttle(spy)
+	})
+	
+	o("runs first call synchronously", function() {
+		throttled()
+		
+		o(spy.callCount).equals(1)
+	})
+	
+	o("throttles subsequent synchronous calls", function(done) {
+		throttled()
+		throttled()
+		
+		o(spy.callCount).equals(1)
+		
+		setTimeout(function() {
+			o(spy.callCount).equals(2)
+			
+			done()
+		}, FRAME_BUDGET) //this delay is much higher than 16.6ms due to setTimeout clamp and other runtime costs
+	})
+	
+	o("calls after threshold", function(done) {
+		throttled()
+		
+		o(spy.callCount).equals(1)
+		
+		setTimeout(function(t) {
+			throttled()
+			
+			o(spy.callCount).equals(2)
+			
+			done()
+		}, FRAME_BUDGET)
+		
+	})
+	
+	o("throttles before threshold", function(done) {
+		throttled()
+		
+		o(spy.callCount).equals(1)
+			
+		callAsync(function(t) {
+			throttled()
+			
+			o(spy.callCount).equals(1)
+			
+			done()
+		})
+	})
+			
+	o("it only runs once per tick", function(done) {
+		throttled()
+		throttled()
+		throttled()
+		
+		o(spy.callCount).equals(1)
+		
+		setTimeout(function() {
+			o(spy.callCount).equals(2)
+			
+			done()
+		}, FRAME_BUDGET)
+	})
+	
+	o("it supports forcing a synchronous redraw", function() {
+		throttled()
+		throttled()
+		throttled(true)
+		
+		o(spy.callCount).equals(2)
+	})
+})