Add clear method to ProtoOutputStream so it is reusable by just
rewinding its internal pointer.

Bug: 72319159
Test: atest incidentd_test and atest statsd_test
Change-Id: Id046b987a7460d68300e5d4d46ae56aec1eba2d0
diff --git a/libs/protoutil/include/android/util/ProtoOutputStream.h b/libs/protoutil/include/android/util/ProtoOutputStream.h
index faea9b2..52830d3 100644
--- a/libs/protoutil/include/android/util/ProtoOutputStream.h
+++ b/libs/protoutil/include/android/util/ProtoOutputStream.h
@@ -123,6 +123,11 @@
     EncodedBuffer::iterator data(); // Get the reader apis of the data.
     bool flush(int fd); // Flush data directly to a file descriptor.
 
+    /**
+     * Clears the ProtoOutputStream so the buffer can be reused instead of deallocation/allocation again.
+     */
+    void clear();
+
     // Please don't use the following functions to dump protos unless you are familiar with protobuf encoding.
     void writeRawVarint(uint64_t varint);
     void writeLengthDelimitedHeader(uint32_t id, size_t size);