When we trace to file, add eol of each trace message.

BUG=webrtc:4864
TEST=Manual Test with voe_cmd_test
R=pbos@webrtc.org
TBR=kjellander@webrtc.org

The regression is introduced in #8529, Review URL: https://webrtc-codereview.appspot.com/34329004.

Review URL: https://codereview.webrtc.org/1256773002 .

Cr-Commit-Position: refs/heads/master@{#9644}
diff --git a/webrtc/system_wrappers/source/trace_impl.cc b/webrtc/system_wrappers/source/trace_impl.cc
index 25da5a0..ffe79b9 100644
--- a/webrtc/system_wrappers/source/trace_impl.cc
+++ b/webrtc/system_wrappers/source/trace_impl.cc
@@ -402,7 +402,12 @@
       row_count_text_++;
     }
   }
-  trace_file_->Write(msg, length);
+
+  char trace_message[WEBRTC_TRACE_MAX_MESSAGE_SIZE];
+  memcpy(trace_message, msg, length);
+  trace_message[length] = 0;
+  trace_message[length - 1] = '\n';
+  trace_file_->Write(trace_message, length);
   row_count_text_++;
 }