Android: Add a build target chrome/browser/tab:java

This CL adds a build target chrome/browser/tab:java and a dummy class
file to get the build working. This will be used to keep the build
green while a 2-side patch https://crrev.com/c/2102998 lands.

The build target doesn't affect any upstream builds for now. Will be
used for the downstream build only, and updated immediately to be
a real target for the upstream.

TBR=twellington@chromium.org

Bug: 995903
Change-Id: I2941cc0066edc083981ee3e386a7225618a3789f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2146406Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758454}

chrome/browser/tab/BUILD.gn

+# 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.
+
+import("//build/config/android/config.gni")
+import("//build/config/android/rules.gni")
+import("//chrome/android/features/android_library_factory_tmpl.gni")
+import("//chrome/browser/buildflags.gni")
+
+android_library("java") {
+  sources = [ "java/src/org/chromium/chrome/browser/tab/Dummy.java" ]
+}

chrome/browser/tab/java/src/org/chromium/chrome/browser/tab/Dummy.java

+// 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.
+
+package org.chromium.chrome.browser.tab;
+
+/**
+ * Dummy class to get the build working for the new target chrome/browser/tab:java.
+ * TODO(jinsukkim): Remove the class once the real target classes are in place.
+ */
+public class Dummy {}