[battor agent] Don't log all bytes received when reading sample frames

tools/battor_agent/battor_connection_impl.cc

Index: tools/battor_agent/battor_connection_impl.cc
diff --git a/tools/battor_agent/battor_connection_impl.cc b/tools/battor_agent/battor_connection_impl.cc
index cf33c2ab97b18e1359f077f192117aae2840b6b5..849637bf8dde71fedc214c68684084137b17aa9c 100644
--- a/tools/battor_agent/battor_connection_impl.cc
+++ b/tools/battor_agent/battor_connection_impl.cc
@@ -228,9 +228,17 @@ void BattOrConnectionImpl::OnBytesRead(int bytes_read,
     return;
   }
 
-  LogSerial(StringPrintf(
-      "%d more bytes read: %s.", bytes_read,
-      CharArrayToString(pending_read_buffer_->data(), bytes_read).c_str()));
+  if (pending_read_message_type_ == BATTOR_MESSAGE_TYPE_SAMPLES) {
+    // If we're reading samples, don't log every byte that we receive. This
+    // exacerbates a problem on Mac wherein we can't process sample frames
+    // quickly enough to prevent the serial buffer from overflowing, causing us
+    // to drop frames.
+    LogSerial(StringPrintf("%d more bytes read.", bytes_read));
+  } else {
+    LogSerial(StringPrintf(
+        "%d more bytes read: %s.", bytes_read,
+        CharArrayToString(pending_read_buffer_->data(), bytes_read).c_str()));
+  }
 
   already_read_buffer_.insert(already_read_buffer_.end(),
                               pending_read_buffer_->data(),