test: Break 'page.spec.js' to smaller files (#2218)

This patch breaks huge `page.spec.js` into a bunch of smaller files.

test/tracing.spec.js

@@ -0,0 +1,56 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require('fs');
+const path = require('path');
+
+module.exports.addTests = function({testRunner, expect}) {
+  const {describe, xdescribe, fdescribe} = testRunner;
+  const {it, fit, xit} = testRunner;
+  const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
+
+  describe('Tracing', function() {
+    beforeEach(function(state) {
+      state.outputFile = path.join(__dirname, 'assets', `trace-${state.parallelIndex}.json`);
+    });
+    afterEach(function(state) {
+      fs.unlinkSync(state.outputFile);
+      state.outputFile = null;
+    });
+    it('should output a trace', async({page, server, outputFile}) => {
+      await page.tracing.start({screenshots: true, path: outputFile});
+      await page.goto(server.PREFIX + '/grid.html');
+      await page.tracing.stop();
+      expect(fs.existsSync(outputFile)).toBe(true);
+    });
+    it('should run with custom categories if provided', async({page, outputFile}) => {
+      await page.tracing.start({path: outputFile, categories: ['disabled-by-default-v8.cpu_profiler.hires']});
+      await page.tracing.stop();
+
+      const traceJson = JSON.parse(fs.readFileSync(outputFile));
+      expect(traceJson.metadata['trace-config']).toContain('disabled-by-default-v8.cpu_profiler.hires');
+    });
+    it('should throw if tracing on two pages', async({page, server, browser, outputFile}) => {
+      await page.tracing.start({path: outputFile});
+      const newPage = await browser.newPage();
+      let error = null;
+      await newPage.tracing.start({path: outputFile}).catch(e => error = e);
+      await newPage.close();
+      expect(error).toBeTruthy();
+      await page.tracing.stop();
+    });
+  });
+};