Separate clear stack and run it after each spec

[finishes #50197985][fix #109418332]
- Fixes #985
- Fixes #945
- Fixes #366

spec/core/ClearStackSpec.js

@@ -0,0 +1,73 @@
+describe("ClearStack", function() {
+  it("works in an integrationy way", function(done) {
+    var global = {
+          setTimeout: typeof setTimeout === 'undefined' ? undefined : setTimeout,
+          setImmediate: typeof setImmediate === 'undefined' ? undefined : setImmediate,
+          MessageChannel: typeof MessageChannel === 'undefined' ? undefined : MessageChannel,
+          process: typeof process === 'undefined' ? undefined : process
+        },
+        clearStack = jasmineUnderTest.getClearStack(global);
+
+    clearStack(function() {
+      done();
+    });
+  });
+
+  it("uses nextTick when available", function() {
+    var nextTick = jasmine.createSpy('nextTick').and.callFake(function(fn) { fn() }),
+        global = { process: { nextTick: nextTick } },
+        clearStack = jasmineUnderTest.getClearStack(global),
+        called = false;
+
+    clearStack(function() {
+      called = true;
+    });
+
+    expect(called).toBe(true);
+    expect(nextTick).toHaveBeenCalled();
+  });
+
+  it("uses setImmediate when available", function() {
+    var setImmediate = jasmine.createSpy('setImmediate').and.callFake(function(fn) { fn() }),
+        global = { setImmediate: setImmediate },
+        clearStack = jasmineUnderTest.getClearStack(global),
+        called = false;
+
+    clearStack(function() {
+      called = true;
+    });
+
+    expect(called).toBe(true);
+    expect(setImmediate).toHaveBeenCalled();
+  });
+
+  it("uses MessageChannels when available", function() {
+    var fakeChannel = {
+          port1: {},
+          port2: { postMessage: function() { fakeChannel.port1.onmessage(); } }
+        },
+        global = { MessageChannel: function() { return fakeChannel; } },
+        clearStack = jasmineUnderTest.getClearStack(global),
+        called = false;
+
+    clearStack(function() {
+      called = true;
+    });
+
+    expect(called).toBe(true);
+  });
+
+  it("falls back to setTimeout", function() {
+    var setTimeout = jasmine.createSpy('setTimeout').and.callFake(function(fn) { fn() }),
+        global = { setTimeout: setTimeout },
+        clearStack = jasmineUnderTest.getClearStack(global),
+        called = false;
+
+    clearStack(function() {
+      called = true;
+    });
+
+    expect(called).toBe(true);
+    expect(setTimeout).toHaveBeenCalledWith(jasmine.any(Function), 0);
+  });
+});