Make dart:developer log more user friendly

runtime/lib/developer.dart

Index: runtime/lib/developer.dart
diff --git a/runtime/lib/developer.dart b/runtime/lib/developer.dart
index 529c53ac0803db3ada0016ba428b73e5f96ed028..f5a4a0022dbd6319bf8121a040677cdead5d9cb0 100644
--- a/runtime/lib/developer.dart
+++ b/runtime/lib/developer.dart
@@ -7,11 +7,45 @@ patch bool debugger({bool when: true,
 
 patch Object inspect(Object object) native "Developer_inspect";
 
-patch log({int sequenceNumber,
-           int millisecondsSinceEpoch,
-           int level,
-           String name,
-           String message,
+patch log(String message,
+          {DateTime time,
+           int sequenceNumber,
+           int level: 0,
+           String name: '',
            Zone zone,
            Object error,
-           StackTrace stackTrace}) native "Developer_log";
+           StackTrace stackTrace}) {
+  if (message is! String) {
+    throw new ArgumentError(message, "message", "Must be a String");
+  }
+  if (time == null) {
+    time = new DateTime.now();
+  }
+  if (time is! DateTime) {
+    throw new ArgumentError(time, "time", "Must be a DateTime");
+  }
+  if (sequenceNumber == null) {
+    sequenceNumber = _nextSequenceNumber;
+  } else {
+    _nextSequenceNumber = sequenceNumber + 1;
+  }
+  return _log(message,
+              time.millisecondsSinceEpoch,
+              sequenceNumber,
+              level,
+              name,
+              zone,
+              error,
+              stackTrace);
+}
+
+int _nextSequenceNumber = 0;
+
+_log(String message,
+     int timestamp,
+     int sequenceNumber,
+     int level,
+     String name,
+     Zone zone,
+     Object error,
+     StackTrace stackTrace) native "Developer_log";