Implement HTTP callbacks in realtime

Hopefully this will improve our recovery time after a laptop is suspended. The
idea is to treat the timeouts on the http apis as being in realtime, rather
than in elapsed time while the machine is awake.

To do this, we add a layer on top of window.setTimeout. We run a callback every
second, which then checks the wallclock time and runs any pending callbacks.

spec/unit/realtime-callbacks.spec.js

@@ -0,0 +1,179 @@
+"use strict";
+
+var callbacks = require("../../lib/realtime-callbacks");
+var test_utils = require("../test-utils.js");
+
+describe("realtime-callbacks", function() {
+    var clock = jasmine.Clock;
+    var fakeDate;
+
+    function tick(millis) {
+        // make sure we tick the fakedate first, otherwise nothing will happen!
+        fakeDate += millis;
+        clock.tick(millis);
+    }
+
+    beforeEach(function() {
+        test_utils.beforeEach(this);
+        clock.useMock();
+        fakeDate = Date.now();
+        callbacks.setNow(function() { return fakeDate; });
+    });
+
+    afterEach(function() {
+        callbacks.setNow();
+    });
+
+    describe("setTimeout", function() {
+        it("should call the callback after the timeout", function() {
+            var callback = jasmine.createSpy();
+            callbacks.setTimeout(callback, 100);
+
+            expect(callback).not.toHaveBeenCalled();
+            tick(100);
+            expect(callback).toHaveBeenCalled();
+        });
+
+
+        it("should default to a zero timeout", function() {
+            var callback = jasmine.createSpy();
+            callbacks.setTimeout(callback);
+
+            expect(callback).not.toHaveBeenCalled();
+            tick(0);
+            expect(callback).toHaveBeenCalled();
+        });
+
+        it("should pass any parameters to the callback", function() {
+            var callback = jasmine.createSpy();
+            callbacks.setTimeout(callback, 0, "a", "b", "c");
+            tick(0);
+            expect(callback).toHaveBeenCalledWith("a", "b", "c");
+        });
+
+        it("should set 'this' to the global object", function() {
+            var callback = jasmine.createSpy();
+            callback.andCallFake(function() {
+                expect(this).toBe(global);
+                expect(this.console).toBeDefined();
+            });
+            callbacks.setTimeout(callback);
+            tick(0);
+            expect(callback).toHaveBeenCalled();
+        });
+
+        it("should handle timeouts of several seconds", function() {
+            var callback = jasmine.createSpy();
+            callbacks.setTimeout(callback, 2000);
+
+            expect(callback).not.toHaveBeenCalled();
+            for (var i = 0; i < 4; i++) {
+                tick(500);
+            }
+            expect(callback).toHaveBeenCalled();
+        });
+
+        it("should call multiple callbacks in the right order", function() {
+            var callback1 = jasmine.createSpy("callback1");
+            var callback2 = jasmine.createSpy("callback2");
+            var callback3 = jasmine.createSpy("callback3");
+            callbacks.setTimeout(callback2, 200);
+            callbacks.setTimeout(callback1, 100);
+            callbacks.setTimeout(callback3, 300);
+
+            expect(callback1).not.toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+            expect(callback3).not.toHaveBeenCalled();
+            tick(100);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+            expect(callback3).not.toHaveBeenCalled();
+            tick(100);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).toHaveBeenCalled();
+            expect(callback3).not.toHaveBeenCalled();
+            tick(100);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).toHaveBeenCalled();
+            expect(callback3).toHaveBeenCalled();
+        });
+
+        it("should treat -ve timeouts the same as a zero timeout", function() {
+            var callback1 = jasmine.createSpy("callback1");
+            var callback2 = jasmine.createSpy("callback2");
+
+            // check that cb1 is called before cb2
+            callback1.andCallFake(function() {
+                expect(callback2).not.toHaveBeenCalled();
+            });
+
+            callbacks.setTimeout(callback1);
+            callbacks.setTimeout(callback2, -100);
+
+            expect(callback1).not.toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+            tick(0);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).toHaveBeenCalled();
+        });
+
+        it("should not get confused by chained calls", function() {
+            var callback2 = jasmine.createSpy("callback2");
+            var callback1 = jasmine.createSpy("callback1");
+            callback1.andCallFake(function() {
+                callbacks.setTimeout(callback2, 0);
+                expect(callback2).not.toHaveBeenCalled();
+            });
+
+            callbacks.setTimeout(callback1);
+            expect(callback1).not.toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+            tick(0);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).toHaveBeenCalled();
+        });
+
+        it("should be immune to exceptions", function() {
+            var callback1 = jasmine.createSpy("callback1");
+            callback1.andCallFake(function() {
+                throw new Error("prepare to die");
+            });
+            var callback2 = jasmine.createSpy("callback2");
+            callbacks.setTimeout(callback1, 0);
+            callbacks.setTimeout(callback2, 0);
+
+            expect(callback1).not.toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+            tick(0);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).toHaveBeenCalled();
+        });
+
+    });
+
+    describe("cancelTimeout", function() {
+        it("should cancel a pending timeout", function() {
+            var callback = jasmine.createSpy();
+            var k = callbacks.setTimeout(callback);
+            callbacks.clearTimeout(k);
+            tick(0);
+            expect(callback).not.toHaveBeenCalled();
+        });
+
+        it("should not affect sooner timeouts", function() {
+            var callback1 = jasmine.createSpy("callback1");
+            var callback2 = jasmine.createSpy("callback2");
+
+            callbacks.setTimeout(callback1, 100);
+            var k = callbacks.setTimeout(callback2, 200);
+            callbacks.clearTimeout(k);
+
+            tick(100);
+            expect(callback1).toHaveBeenCalled();
+            expect(callback2).not.toHaveBeenCalled();
+
+            tick(150);
+            expect(callback2).not.toHaveBeenCalled();
+        });
+    });
+});