Use Zone to correctly measure async operations.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 950b4258588442ed79315f5d1c4bb4e528c6c231..36ceefa63aa824407a0571070e5d24910e169a43 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -2207,21 +2207,67 @@ class CompilerTask {
 
   int get timingMicroseconds => (watch != null) ? watch.elapsedMicroseconds : 0;
 
-  measure(action()) {
-    // In verbose mode when watch != null.
-    if (watch == null) return action();
+  measure(action()) => watch == null ? action() : measureZoned(action);

[Johnni Winther, 2015/11/19 10:02:18]

Add doc

+
+  CompilerTask start() {

[Johnni Winther, 2015/11/19 10:02:18]

Add doc

     CompilerTask previous = compiler.measuredTask;
-    if (identical(this, previous)) return action();
     compiler.measuredTask = this;
     if (previous != null) previous.watch.stop();
     watch.start();
-    try {
-      return action();
-    } finally {
-      watch.stop();
-      if (previous != null) previous.watch.start();
-      compiler.measuredTask = previous;
+    return previous;
+  }
+
+  void stop(CompilerTask previous) {

[Johnni Winther, 2015/11/19 10:02:18]

Add doc

+    watch.stop();
+    if (previous != null) previous.watch.start();
+    compiler.measuredTask = previous;
+  }
+
+  measureZoned(action()) {

[Johnni Winther, 2015/11/19 10:02:18]

Add doc.

+    assert(watch != null);
+    if (identical(this, compiler.measuredTask)) return action();
+
+    run(Zone self, ZoneDelegate parent, Zone zone, f()) {
+      CompilerTask previous = start();
+      try {
+        return f();
+      } finally {
+        stop(previous);
+      }
     }
+
+    runUnary(Zone self, ZoneDelegate parent, Zone zone, f(arg), arg) {
+      CompilerTask previous = start();
+      try {
+        return f(arg);
+      } finally {
+        stop(previous);
+      }
+    }
+
+    runBinary(Zone self, ZoneDelegate parent, Zone zone, f(a1, a2), a1, a2) {
+      CompilerTask previous = start();
+      try {
+        return f(a1, a2);
+      } finally {
+        stop(previous);
+      }
+    }
+
+    return runZoned(
+        action, zoneSpecification: new ZoneSpecification(
+            run: run, runUnary: runUnary, runBinary: runBinary));
+  }
+
+  measureIo(action()) => watch == null ? action() : measureIoHelper(action);

[Johnni Winther, 2015/11/19 10:02:18]

Add doc

+
+  Future measureIoHelper(Future action()) {
+    assert(watch != null);
+    if (identical(this, compiler.measuredTask)) return action();
+    CompilerTask previous = start();
+    return measure(action).whenComplete(() {
+      stop(previous);
+    });
   }
 
   measureElement(Element element, action()) {