Create protoc-gen-cppstream tool to auto-generate cpp proto field Ids.

It is very similiar to protoc-gen-javastream, which generates field Ids used
by ProtoOutputStream.cpp to dump protobuf data.

Bug: 65641021
Test: compile the streaming_proto:
      $ mmm -j frameworks/base/tools/streaming_proto/
      and run:
      $ PATH=$PATH:out/host/linux-x86/bin/protoc-gen-cppstream aprotoc
      --cppstream_out=tmp/
      frameworks/base/core/proto/android/service/procstats.proto
      frameworks/base/core/proto/android/util/common.proto

Change-Id: I68becc80b5166455455c5df28cd698601b4a1c1d
diff --git a/tools/streaming_proto/Android.bp b/tools/streaming_proto/Android.bp
index 24068e9..756549c 100644
--- a/tools/streaming_proto/Android.bp
+++ b/tools/streaming_proto/Android.bp
@@ -17,13 +17,31 @@
 // ==========================================================
 // Build the host executable: protoc-gen-javastream
 // ==========================================================
-cc_binary_host {
-    name: "protoc-gen-javastream",
+cc_defaults {
+    name: "protoc-gen-stream-defaults",
     srcs: [
         "Errors.cpp",
         "string_utils.cpp",
-        "main.cpp",
+    ],
+}
+
+
+cc_binary_host {
+    name: "protoc-gen-javastream",
+    srcs: [
+        "java/main.cpp",
     ],
 
+    defaults: ["protoc-gen-stream-defaults"],
+    shared_libs: ["libprotoc"],
+}
+
+cc_binary_host {
+    name: "protoc-gen-cppstream",
+    srcs: [
+        "cpp/main.cpp",
+    ],
+
+    defaults: ["protoc-gen-stream-defaults"],
     shared_libs: ["libprotoc"],
 }