Partially externalize WebDriver tests

This change does a few things:

  1. Partially externalized WebDriver tests by using ChromeDriver
     as an implementation of WebDriver API in the external build.
  2. Refactored WebDriverRule.java to decouple the creation and
     using of WebDriver related stuff so we can have different
     implementations in internal and external builds.
  3. Refactored the usage of some internal libraries to have a
     central place to store all of them to make it easier to
     remove them in the external build.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=233661757

javatests/google/registry/webdriver/ChromeWebDriverPlusScreenDiffer.java

@@ -0,0 +1,71 @@
+// Copyright 2019 The Nomulus Authors. 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.
+
+package google.registry.webdriver;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import org.openqa.selenium.WebDriver;
+import org.openqa.selenium.WebElement;
+import org.openqa.selenium.chrome.ChromeDriver;
+import org.openqa.selenium.chrome.ChromeDriverService;
+import org.openqa.selenium.chrome.ChromeOptions;
+
+/** Implementation of {@link WebDriverPlusScreenDiffer} that uses {@link ChromeDriver}. */
+class ChromeWebDriverPlusScreenDiffer implements WebDriverPlusScreenDiffer {
+
+  private static final ChromeDriverService chromeDriverService = createChromeDriverService();
+  private final WebDriver webDriver;
+
+  public ChromeWebDriverPlusScreenDiffer() {
+    ChromeOptions chromeOptions = new ChromeOptions();
+    chromeOptions.setHeadless(true);
+    webDriver = new ChromeDriver(chromeDriverService, chromeOptions);
+  }
+
+  private static ChromeDriverService createChromeDriverService() {
+    ChromeDriverService chromeDriverService =
+        new ChromeDriverService.Builder().usingAnyFreePort().build();
+    try {
+      chromeDriverService.start();
+    } catch (IOException e) {
+      throw new UncheckedIOException(e);
+    }
+    Runtime.getRuntime().addShutdownHook(new Thread(chromeDriverService::stop));
+    return chromeDriverService;
+  }
+
+  @Override
+  public WebDriver getWebDriver() {
+    return webDriver;
+  }
+
+  @Override
+  public void diffElement(String imageKey, WebElement element) {
+    // TODO(b/122650673): Add implementation for screenshots comparison. It is no-op
+    //   right now to prevent the test failure.
+  }
+
+  @Override
+  public void diffPage(String imageKey) {
+    // TODO(b/122650673): Add implementation for screenshots comparison. It is no-op
+    //   right now to prevent the test failure.
+  }
+
+  @Override
+  public void verifyAndQuit() {
+    // TODO(b/122650673): Add implementation for screenshots comparison. It is no-op
+    //   right now to prevent the test failure.
+  }
+}