Fixig issues in BWE dynamics plot scripts.

BUG=None

Review-Url: https://codereview.webrtc.org/2360053003
Cr-Commit-Position: refs/heads/master@{#14459}
diff --git a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
index b336367..a1f1fd3 100644
--- a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
+++ b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
@@ -180,7 +180,7 @@
     rtc::CritScope cs(&critsect_);
     bandwidth_estimation_.UpdateReceiverEstimate(clock_->TimeInMilliseconds(),
                                                  bitrate);
-    BWE_TEST_LOGGING_PLOT(1, "REMB[kbps]", clock_->TimeInMilliseconds(),
+    BWE_TEST_LOGGING_PLOT(1, "REMB_kbps", clock_->TimeInMilliseconds(),
                           bitrate / 1000);
   }
   MaybeTriggerOnNetworkChanged();
@@ -269,11 +269,11 @@
     new_bitrate = true;
   }
 
-  BWE_TEST_LOGGING_PLOT(1, "fraction_loss_[%%]", clock_->TimeInMilliseconds(),
+  BWE_TEST_LOGGING_PLOT(1, "fraction_loss_%", clock_->TimeInMilliseconds(),
                         (last_fraction_loss_ * 100) / 256);
-  BWE_TEST_LOGGING_PLOT(1, "rtt[ms]", clock_->TimeInMilliseconds(),
+  BWE_TEST_LOGGING_PLOT(1, "rtt_ms", clock_->TimeInMilliseconds(),
                         last_rtt_ms_);
-  BWE_TEST_LOGGING_PLOT(1, "Target_bitrate[kbps]", clock_->TimeInMilliseconds(),
+  BWE_TEST_LOGGING_PLOT(1, "Target_bitrate_kbps", clock_->TimeInMilliseconds(),
                         last_bitrate_bps_ / 1000);
 
   return new_bitrate;