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 09ab8e58963af245e88d46fe9d4a0bf6359aad5f..11cf2051c3496ace8dea98d7de791c24c626e376 100644
--- a/pkg/compiler/lib/src/dump_info.dart
+++ b/pkg/compiler/lib/src/dump_info.dart
@@ -565,7 +565,7 @@ class DumpInfoTask extends CompilerTask implements InfoReporter {
         size: _programSize,
         dart2jsVersion: compiler.hasBuildId ? compiler.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,