Added expectAsync(...).already

* Causes async matchers to immediately fail if the promise is pending
* Fixes #1845

src/core/base.js

@@ -203,6 +203,19 @@ getJasmineRequireObj().base = function(j$, jasmineGlobal) {
     return matches ? matches[1] : '<anonymous>';
   };
 
+  j$.isPending_ = function(promise) {
+    var sentinel = {};
+    // eslint-disable-next-line compat/compat
+    return Promise.race([promise, Promise.resolve(sentinel)]).then(
+      function(result) {
+        return result === sentinel;
+      },
+      function() {
+        return false;
+      }
+    );
+  };
+
   /**
    * Get a matcher, usable in any {@link matchers|matcher} that uses Jasmine's equality (e.g. {@link matchers#toEqual|toEqual}, {@link matchers#toContain|toContain}, or {@link matchers#toHaveBeenCalledWith|toHaveBeenCalledWith}),
    * that will succeed if the actual value being compared is an instance of the specified class/constructor.