Bug 1205938 part 1 - Add waitForCondition() function to SimpleTest. r=jmaher

This function is roughly copied from browser/base/content/test/general/head.js.
It has been widely used in browser chrome mochitests, and should be fine to
have it available to all mochitests via SimpleTest.

MozReview-Commit-ID: DhIfgJiUhXK

--HG--
extra : rebase_source : 95ab1cd6c1ab5f6c0d8f0171865722ca76b41c6e

dom/plugins/test/mochitest/test_bug751809.html

@@ -23,21 +23,6 @@
   const utils = window.QueryInterface(Ci.nsIInterfaceRequestor).
                                     getInterface(Ci.nsIDOMWindowUtils);
 
-  function waitForCondition(condition, nextTest, errorMsg) {
-    var tries = 0;
-    var interval = setInterval(function() {
-      if (tries >= 30) {
-        ok(false, errorMsg);
-        moveOn();
-      }
-      if (condition()) {
-        moveOn();
-      }
-      tries++;
-    }, 100);
-    var moveOn = function() { clearInterval(interval); nextTest(); };
-  }
-
   function go() {
     var plugin = document.getElementById('plugin');
     var objLoadingContent = SpecialPowers.wrap(plugin);
@@ -52,7 +37,8 @@
 
     objLoadingContent.playPlugin();
     var condition = () => plugin.setColor !== undefined;
-    waitForCondition(condition, afterPluginActivation, "Waited too long for plugin to activate");
+    SimpleTest.waitForCondition(condition, afterPluginActivation,
+                                "Waited too long for plugin to activate");
   }
     
   function afterPluginActivation() {
@@ -77,7 +63,8 @@
 
     synthesizeMouseAtCenter(plugin, {});
     var condition = () => plugin.getMouseUpEventCount() > 0;
-    waitForCondition(condition, afterFirstClick, "Waited too long for plugin to receive the mouse click");
+    SimpleTest.waitForCondition(condition, afterFirstClick,
+                                "Waited too long for plugin to receive the mouse click");
   }
 
   function afterFirstClick() {

testing/mochitest/tests/SimpleTest/SimpleTest.js

@@ -973,6 +973,45 @@ SimpleTest.waitForClipboard = function(aExpectedStringOrValidatorFn, aSetupFn,
          }, aFailureFn, "text/unicode");
 }
 
+/**
+ * Wait for a condition for a while (actually up to 3s here).
+ *
+ * @param aCond
+ *        A function returns the result of the condition
+ * @param aCallback
+ *        A function called after the condition is passed or timeout.
+ * @param aErrorMsg
+ *        The message displayed when the condition failed to pass
+ *        before timeout.
+ */
+SimpleTest.waitForCondition = function (aCond, aCallback, aErrorMsg) {
+  var tries = 0;
+  var interval = setInterval(() => {
+    if (tries >= 30) {
+      ok(false, aErrorMsg);
+      moveOn();
+      return;
+    }
+    var conditionPassed;
+    try {
+      conditionPassed = aCond();
+    } catch (e) {
+      ok(false, `${e}\n${e.stack}`);
+      conditionPassed = false;
+    }
+    if (conditionPassed) {
+      moveOn();
+    }
+    tries++;
+  }, 100);
+  var moveOn = () => { clearInterval(interval); aCallback(); };
+};
+SimpleTest.promiseWaitForCondition = function (aCond, aErrorMsg) {
+  return new Promise(resolve => {
+    this.waitForCondition(aCond, resolve, aErrorMsg);
+  });
+};
+
 /**
  * Executes a function shortly after the call, but lets the caller continue
  * working (or finish).