Revert "Refactor Reader Mode's JavaScript tests to use Mocha."

This reverts commit 7de90169.

Reason for revert: Suspicious to have broken DomDistillerViewerSourceBrowserTest.UISetsPrefs in browser_tests.
https://ci.chromium.org/p/chromium/builders/ci/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/37476


Original change's description:
> Refactor Reader Mode's JavaScript tests to use Mocha.
> 
> The tests did not previously use an established test framework, making
> tasks like executing certain code before or after every test and testing
> asynchronous code more difficult. It should also be easier for
> developers familiar with JavaScript testing in general and WebUI testing
> in particular to read and write JavaScript tests for DOM Distiller and
> Reader Mode.
> 
> Follow-up work includes replacing the custom assert methods with Chai,
> as well as writing more tests to cover existing functionality.
> 
> Bug: 1027612
> Change-Id: I39acc923a0424881d2694281d9aa0323c8f9a913
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992504
> Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
> Commit-Queue: Aran Gilman <gilmanmh@google.com>
> Cr-Commit-Position: refs/heads/master@{#762551}

TBR=wychen@chromium.org,gilmanmh@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1027612
Change-Id: I78b6b82e98c8f47951ab88e2056595de878f1ab1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2166219Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762720}

components/BUILD.gn

@@ -561,7 +561,6 @@ if (!is_ios && !is_fuchsia) {
       "security_state/content/testdata/",
       "//content/test/data/",
       "//third_party/dom_distiller_js/dist/test/data/",
-      "//third_party/mocha",
     ]
 
     deps = [

components/dom_distiller/content/browser/test/distilled_page_js_browsertest.cc

@@ -22,6 +22,22 @@
 namespace dom_distiller {
 namespace {
 
+base::Value ExecuteJsScript(content::WebContents* web_contents,
+                            const std::string& script) {
+  base::Value result;
+  base::RunLoop run_loop;
+  web_contents->GetMainFrame()->ExecuteJavaScriptForTests(
+      base::UTF8ToUTF16(script),
+      base::BindOnce(
+          [](base::Closure callback, base::Value* out, base::Value result) {
+            (*out) = std::move(result);
+            callback.Run();
+          },
+          run_loop.QuitClosure(), &result));
+  run_loop.Run();
+  return result;
+}
+
 class DistilledPageJsTest : public content::ContentBrowserTest {
  protected:
   explicit DistilledPageJsTest()
@@ -37,13 +53,14 @@ class DistilledPageJsTest : public content::ContentBrowserTest {
     distilled_page_ = SetUpTestServerWithDistilledPage(embedded_test_server());
   }
 
-  void LoadAndExecuteTestScript(const std::string& file) {
+  void LoadAndExecuteTestScript(const std::string& file,
+                                const std::string& fixture_name) {
     distilled_page_->AppendScriptFile(file);
     distilled_page_->Load(embedded_test_server(), shell()->web_contents());
-    bool allTestsPassed;
-    ASSERT_TRUE(content::ExecuteScriptAndExtractBool(
-        shell()->web_contents(), "mocha.run()", &allTestsPassed));
-    EXPECT_TRUE(allTestsPassed);
+    const base::Value result = ExecuteJsScript(
+        shell()->web_contents(), base::StrCat({fixture_name, ".run()"}));
+    ASSERT_EQ(base::Value::Type::BOOLEAN, result.type());
+    EXPECT_TRUE(result.GetBool());
   }
 
   std::unique_ptr<FakeDistilledPage> distilled_page_;
@@ -55,7 +72,7 @@ class DistilledPageJsTest : public content::ContentBrowserTest {
 #define MAYBE_Pinch Pinch
 #endif
 IN_PROC_BROWSER_TEST_F(DistilledPageJsTest, MAYBE_Pinch) {
-  LoadAndExecuteTestScript("pinch_tester.js");
+  LoadAndExecuteTestScript("pinch_tester.js", "pinchtest");
 }
 
 }  // namespace

components/dom_distiller/content/browser/test/test_util.cc

@@ -39,12 +39,10 @@ const char* kDistilledPagePath = "/distilled_page.html";
 void SetUpTestServerWithoutStarting(EmbeddedTestServer* server) {
   FilePath root_dir;
   PathService::Get(base::DIR_SOURCE_ROOT, &root_dir);
-
-  server->ServeFilesFromDirectory(
-      root_dir.AppendASCII("components/dom_distiller/core/javascript"));
   server->ServeFilesFromDirectory(
       root_dir.AppendASCII("components/test/data/dom_distiller"));
-  server->ServeFilesFromDirectory(root_dir.AppendASCII("third_party/mocha"));
+  server->ServeFilesFromDirectory(
+      root_dir.AppendASCII("components/dom_distiller/core/javascript"));
 }
 
 }  // namespace
@@ -60,8 +58,6 @@ FakeDistilledPage::FakeDistilledPage(EmbeddedTestServer* server)
   // DomDistillerRequestViewBase::SendCommonJavaScript(); however, this method
   // is impractical to use in testing.
   AppendScriptFile("dom_distiller_viewer.js");
-  AppendScriptFile("mocha.js");
-  AppendScriptFile("test_util.js");
 }
 
 FakeDistilledPage::~FakeDistilledPage() = default;

components/test/data/dom_distiller/test_util.js

-// Copyright 2020 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Based on BrowserTestReporter() in //chrome/test/data/webui/mocha_adapter.js
-// TODO(crbug.com/1027612): Look into using that class directly.
-function TestReporter(runner) {
-  let passes = 0;
-  let failures = 0;
-
-  runner.on('pass', function(test) {
-    passes++;
-  });
-
-  runner.on('fail', function(test, err) {
-    failures++;
-    let message = 'Mocha test failed: ' + test.fullTitle() + '\n';
-
-    // Remove unhelpful mocha lines from stack trace.
-    if (err.stack) {
-      const stack = err.stack.split('\n');
-      for (let i = 0; i < stack.length; i++) {
-        if (stack[i].indexOf('mocha.js:') == -1) {
-          message += stack[i] + '\n';
-        }
-      }
-    } else {
-      message += err.toString();
-    }
-
-    console.error(message);
-  });
-
-  runner.on('end', function() {
-    window.domAutomationController.send(failures === 0 && passes > 0);
-  });
-}
-
-mocha.setup({
-  ui: 'tdd',
-  reporter: TestReporter,
-  enableTimeouts: false,
-});