Let stopwatch use window.performance.now when available. Fix for: http://code.google.com/p/dart/iss…

sdk/lib/_internal/compiler/implementation/lib/core_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
index 5c6cb3bbe6ee7f8a38ba7532fc3d4730c0287a00..017df881bd271e02713f6e61c63b5ae633d558f6 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/core_patch.dart
@@ -149,7 +149,7 @@ patch class _DateImpl {
 // Patch for Stopwatch implementation.
 patch class _StopwatchImpl {
   patch static int _frequency() => 1000;

[kasperl, 2012/11/21 10:27:57]

Wouldn't it be nicer if we returned 1000000 if we can use the high-resolution
timer (window.performance.now) and 1000 if we need to fall back on Date.now()?
That way, we don't need to multiply by 1000 in case we use Date.now() which
seems nicer.

-  patch static int _now() => Primitives.dateNow();
+  patch static int _now() => Primitives.numMicroseconds();
 }