CSSPaint: Move layout tests in csspaint/ to http/tests/csspaint/

third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-helper.js

-// Given a set of 'tests', runs them in the worklet, then comparing the
-// expectedError or the expectedMessage.
-//
-// Usage:
-//   runner([{/* test1 */}, { /* test2 */}]);
-function runner(tests) {
-    if (window.testRunner) {
-        testRunner.waitUntilDone();
-        testRunner.dumpAsText();
-    }
-
-    tests.reduce(function(chain, obj) {
-        return chain.then(function() {
-            if (obj.expectedError) {
-                console.log('The worklet should throw an error with: "' + obj.expectedError + '"');
-            } else if (obj.expectedMessage) {
-                console.log('The worklet should log a warning with: "' + obj.expectedMessage + '"');
-            } else {
-                console.log('The worklet should not throw an error.');
-            }
-            var blob = new Blob([obj.script], {type: 'text/javascript'});
-            return paintWorklet.addModule(URL.createObjectURL(blob));
-        });
-    }, Promise.resolve()).then(function() {
-        if (window.testRunner) {
-            testRunner.notifyDone();
-        }
-    });
-}