Mark FancyTerminalEventHandler.handle() as synchronized. A previous change
removed "sychronized" from Reporter.handle() as we want to be able to let
EventHandlers care about their own synchronization.

RELNOTES: None.
PiperOrigin-RevId: 208628638
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/FancyTerminalEventHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/FancyTerminalEventHandler.java
index 90975de..1154c62 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/FancyTerminalEventHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/FancyTerminalEventHandler.java
@@ -128,7 +128,7 @@
   }
 
   @Override
-  public void handle(Event event) {
+  public synchronized void handle(Event event) {
     if (terminalClosed) {
       return;
     }