android: Add the target to toplevel Looper events in tracing,

base/android/java/src/org/chromium/base/TraceEvent.java

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.base;
 
 import android.os.Looper;
 import android.os.MessageQueue;
 import android.os.SystemClock;
 import android.util.Log;
@@ skipping 20 matching lines @@
         public void println(final String line) {
             if (line.startsWith(">")) {
                 beginHandling(line);
             } else {
                 assert line.startsWith("<");
                 endHandling(line);
             }
         }
 
         void beginHandling(final String line) {
-            if (sEnabled) nativeBeginToplevel();
+            if (sEnabled) {
+                // Android Looper formats |line| as ">>>>> Dispatching to (TARGET) [...]" since at
+                // least 2009 (Donut). Extracts the TARGET part of the message.
+                int start = line.indexOf('(', 21); // strlen(">>>>> Dispatching to ")
+                int end = start == -1 ? -1 : line.indexOf(')', start);
+                String target = end != -1 ? line.substring(start + 1, end) : "";
+                nativeBeginToplevel(target);
+            }
         }
 
         void endHandling(final String line) {
             if (sEnabled) nativeEndToplevel();
         }
     }
 
     /**
      * A class that records, traces and logs statistics about the UI thead's Looper.
      * The output of this class can be used in a number of interesting ways:
@@ skipping 248 matching lines @@
         EarlyTraceEvent.end(name);
         if (sEnabled) nativeEnd(name, arg);
     }
 
     private static native void nativeRegisterEnabledObserver();
     private static native void nativeStartATrace();
     private static native void nativeStopATrace();
     private static native void nativeInstant(String name, String arg);
     private static native void nativeBegin(String name, String arg);
     private static native void nativeEnd(String name, String arg);
-    private static native void nativeBeginToplevel();
+    private static native void nativeBeginToplevel(String target);
     private static native void nativeEndToplevel();
     private static native void nativeStartAsync(String name, long id);
     private static native void nativeFinishAsync(String name, long id);
 }