cronet: add accessor class for CronetChannelBuilder to avoid exposing setTrafficStats* API directly. (#5983)

cronet/src/main/java/io/grpc/cronet/InternalCronetChannelBuilder.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2019 The gRPC Authors
+ *
+ * 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 io.grpc.cronet;
+
+import io.grpc.Internal;
+
+/**
+ * Internal {@link CronetChannelBuilder} accessor. This is intended for usage internal to the gRPC
+ * team. If you *really* think you need to use this, contact the gRPC team first.
+ */
+@Internal
+public class InternalCronetChannelBuilder {
+
+  /**
+   * Sets {@link android.net.TrafficStats} tag to use when accounting socket traffic caused by this
+   * channel. See {@link android.net.TrafficStats} for more information. If no tag is set (e.g. this
+   * method isn't called), then Android accounts for the socket traffic caused by this channel as if
+   * the tag value were set to 0.
+   *
+   * <p><b>NOTE:</b>Setting a tag disallows sharing of sockets with channels with other tags, which
+   * may adversely effect performance by prohibiting connection sharing. In other words use of
+   * multiplexed sockets (e.g. HTTP/2 and QUIC) will only be allowed if all channels have the same
+   * socket tag.
+   */
+  public static void setTrafficStatsTag(CronetChannelBuilder builder, int tag) {
+    builder.setTrafficStatsTag(tag);
+  }
+
+  /**
+   * Sets specific UID to use when accounting socket traffic caused by this channel. See {@link
+   * android.net.TrafficStats} for more information. Designed for use when performing an operation
+   * on behalf of another application. Caller must hold {@link
+   * android.Manifest.permission#MODIFY_NETWORK_ACCOUNTING} permission. By default traffic is
+   * attributed to UID of caller.
+   *
+   * <p><b>NOTE:</b>Setting a UID disallows sharing of sockets with channels with other UIDs, which
+   * may adversely effect performance by prohibiting connection sharing. In other words use of
+   * multiplexed sockets (e.g. HTTP/2 and QUIC) will only be allowed if all channels have the same
+   * UID set.
+   */
+  public static void setTrafficStatsUid(CronetChannelBuilder builder, int uid) {
+    builder.setTrafficStatsUid(uid);
+  }
+}