Add ADB transport skeleton

This adds the AIDL definition for ADB transports. For instance USB is
one type of ADB transport and the only one supported now.

Bug: 63820489
Test: make
Change-Id: Id422a814567021ab4b1097c2792a95c42bfccf74

core/java/android/debug/AdbManagerInternal.java

@@ -23,4 +23,17 @@ package android.debug;
  * @hide Only should be called from the system server.
  */
 public abstract class AdbManagerInternal {
+    /**
+     * Registers a ADB transport mechanism.
+     *
+     * @param transport ADB transport interface to register
+     */
+    public abstract void registerTransport(IAdbTransport transport);
+
+    /**
+     * Unregisters a previously registered ADB transport mechanism.
+     *
+     * @param transport previously-added ADB transport interface to be removed
+     */
+    public abstract void unregisterTransport(IAdbTransport transport);
 }

core/java/android/debug/IAdbTransport.aidl

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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 android.debug;
+
+/** @hide */
+interface IAdbTransport {
+}