TAPL: Tracing only changed part of the context for diags

Printing the whole context stack has proven to be harder to decipher.

Change-Id: Ic11981884491fc96b939f4736ec974a1640c0304

tests/tapl/com/android/launcher3/tapl/LauncherInstrumentation.java

@@ -260,9 +260,9 @@ public final class LauncherInstrumentation {
 
     Closable addContextLayer(String piece) {
         mDiagnosticContext.addLast(piece);
-        log("Added context: " + getContextDescription());
+        log("Entering context: " + piece);
         return () -> {
-            log("Removing context: " + getContextDescription());
+            log("Leaving context: " + piece);
             mDiagnosticContext.removeLast();
         };
     }