Treat should().throw(undefined) like should().throw()

Interpret throw(undefined) to mean that an error of any type is
expected.  This is the same as throw().

BUG=706558
TEST=audit.html

Review-Url: https://codereview.chromium.org/2783033002
Cr-Commit-Position: refs/heads/master@{#460584}

third_party/WebKit/LayoutTests/webaudio/resources/audit.js

@@ -287,7 +287,7 @@ window.Audit = (function () {
         // Catch did not happen, so the test is failed.
         failDetail = '${actual} did not throw an exception.';
       } catch (error) {
-        if (this._expected === null) {
+        if (this._expected === null || this._expected === undefined) {
           // The expected error type was not given.
           didThrowCorrectly = true;
           passDetail = '${actual} threw ' + error.name + ': "'

third_party/WebKit/LayoutTests/webaudio/unit-tests/audit-expected.txt

@@ -21,6 +21,8 @@ PASS   OfflineAudioContext does exist.
 PASS   Setting foo1 to 0 did not throw an exception. 
 PASS   function () { var foo2 = bar; } threw ReferenceError: "bar is not defined". 
 PASS   function () { var foo3 = bar; } threw ReferenceError: "bar is not defined". 
+PASS   function () { var foo4 = bar; } threw ReferenceError: "bar is not defined". 
+PASS   function () { var foo5 = bar; } threw ReferenceError: "bar is not defined". 
 PASS   Calling should() with no argument threw Error: "Task.should:: requires at least 1 argument.". 
 PASS   3 < 5 is true. 
 PASS   false is false. 
@@ -37,7 +39,7 @@ PASS   The message is truthful!
 PASS   Decoding audio data with no argument rejected correctly with TypeError: Failed to execute 'decodeAudioData' on 'BaseAudioContext': 1 argument required, but only 0 present.. 
 PASS   Suspending OAC with no argument rejected correctly with TypeError. 
 PASS   Start OAC rendering resolved correctly. 
-PASS < [basic] All assertions passed. (total 20 assertions) 
+PASS < [basic] All assertions passed. (total 22 assertions) 
 PASS > [load-file-in-should] Test Audit.loadFileFromUrl() within |should| assertion. 
 PASS   Loading file within should().beResolved() resolved correctly. 
 PASS < [load-file-in-should] All assertions passed. (total 1 assertions) 

third_party/WebKit/LayoutTests/webaudio/unit-tests/audit.html

@@ -20,6 +20,8 @@
         should(function () { var foo1 = 0; }, 'Setting foo1 to 0').notThrow();
         should(function () { var foo2 = bar; }).throw();
         should(function () { var foo3 = bar; }).throw('ReferenceError');
+        should(function () { var foo4 = bar; }).throw(null);
+        should(function () { var foo5 = bar; }).throw(undefined);
         should(() => { should(); }, 'Calling should() with no argument')
             .throw('Error');
         should(3 < 5, '3 < 5').beTrue();