feat(firestore): support retrieving documents up to 16MB over gRPC watch stream

Author: dlarocque

firebase-firestore/CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- [changed] Increased the gRPC maximum inbound message size limit to 17MB to support downloading Cloud Firestore documents of up to 16MB.
+
 # 26.4.0
 
 - [feature] Added support for `minimum` and `maximum` FieldValue operations.

firebase-firestore/src/main/java/com/google/firebase/firestore/remote/GrpcCallProvider.java

@@ -57,6 +57,11 @@ public class GrpcCallProvider {
   // reconnecting again, rather than waiting up to 2+ minutes for gRPC to timeout.
   // More details about usage can be found in GrpcCallProvider.onConnectivityStateChanged().
   private static final int CONNECTIVITY_ATTEMPT_TIMEOUT_MS = 15 * 1000;
+
+  // This is used to increase the max inbound message size from the 4MB default to 17MB,
+  // in order to support 16MB docs + overhead.
+  // https://grpc.github.io/grpc-java/javadoc/io/grpc/okhttp/OkHttpServerBuilder.html#maxInboundMessageSize(int)
+  private static final int MAX_INBOUND_MESSAGE_SIZE = 17 * 1024 * 1024;
   private DelayedTask connectivityAttemptTimer;
 
   private final Context context;
@@ -108,6 +113,9 @@ private ManagedChannel initChannel(Context context, DatabaseInfo databaseInfo) {
     // usually notify gRPC when a connection dies. But not always. This acts as a failsafe.)
     channelBuilder.keepAliveTime(30, TimeUnit.SECONDS);
 
+    // Increase the maximum inbound message size from 4MB to 17MB, to support 16MB docs.
+    channelBuilder.maxInboundMessageSize(MAX_INBOUND_MESSAGE_SIZE);
+
     // Wrap the ManagedChannelBuilder in an AndroidChannelBuilder. This allows the channel to
     // respond more gracefully to network change events (such as switching from cell to wifi).
     AndroidChannelBuilder androidChannelBuilder =