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/src/EncodedBuffer.cpp b/libs/protoutil/src/EncodedBuffer.cpp
index 435ae88..3a5e2e9 100644
--- a/libs/protoutil/src/EncodedBuffer.cpp
+++ b/libs/protoutil/src/EncodedBuffer.cpp
@@ -106,6 +106,13 @@
     return mBuffers[p.index()] + p.offset();
 }
 
+void
+EncodedBuffer::clear()
+{
+    mWp.rewind();
+    mEp.rewind();
+}
+
 /******************************** Write APIs ************************************************/
 size_t
 EncodedBuffer::size() const