Use Zone to correctly measure async operations.

pkg/compiler/lib/src/dump_info.dart

Index: pkg/compiler/lib/src/dump_info.dart
diff --git a/pkg/compiler/lib/src/dump_info.dart b/pkg/compiler/lib/src/dump_info.dart
index 54ca88ff770403ac4d4f8ea682f76d38934439dd..854feb1484b2c33664c93cb0a217cc1c0e71bbed 100644
--- a/pkg/compiler/lib/src/dump_info.dart
+++ b/pkg/compiler/lib/src/dump_info.dart
@@ -579,7 +579,7 @@ class DumpInfoTask extends CompilerTask implements InfoReporter {
         dart2jsVersion:
             compiler.options.hasBuildId ? compiler.options.buildId : null,
         compilationMoment: new DateTime.now(),
-        compilationDuration: compiler.totalCompileTime.elapsed,
+        compilationDuration: compiler.measurer.wallClock.elapsed,
         toJsonDuration: stopwatch.elapsedMilliseconds,
         dumpInfoDuration: this.timing,
         noSuchMethodEnabled: compiler.backend.enabledNoSuchMethod,