Add StackTrace.current getter.

sdk/lib/_internal/js_runtime/lib/core_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/core_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index 301517ee669f5a532008375f12048c4f37bc0ba0..2e1037e90c3898166ad5923260dbd71698ada91d 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -5,21 +5,22 @@
 // Patch file for dart:core classes.
 import "dart:_internal" as _symbol_dev;
 import 'dart:_interceptors';
-import 'dart:_js_helper' show patch,
-                              patch_full,
-                              patch_lazy,
-                              patch_startup,
-                              checkInt,
+import 'dart:_js_helper' show checkInt,
+                              Closure,
+                              ConstantMap,
                               getRuntimeType,
+                              JsLinkedHashMap;
                               jsonEncodeNative,
                               JSSyntaxRegExp,
-                              Primitives,
-                              ConstantMap,
-                              stringJoinUnchecked,
+                              NoInline,
                               objectHashCode,
-                              Closure,
+                              patch,
+                              patch_full,
+                              patch_lazy,
+                              patch_startup,
+                              Primitives,
                               readHttp,
-                              JsLinkedHashMap;
+                              stringJoinUnchecked,
 
 import 'dart:_foreign_helper' show JS;
 
@@ -671,3 +672,24 @@ class _Resource implements Resource {
     });
   }
 }
+
+@patch
+class StackTrace {
+  @patch
+  @NoInline()
+  static StackTrace get current {
+    var error = JS('', 'new Error()');
+    var stack = JS('String|Null', '#.stack', error);
+    if (stack is String) return new StackTrace.fromString(stack);
+    if (JS('', 'Error.captureStackTrace') != null) {
+      JS('void', 'Error.captureStackTrace(#)', error);
+      var stack = JS('String|Null', '#.stack', error);
+      if (stack is String) return new StackTrace.fromString(stack);
+    }
+    try {
+      throw 0;
+    } catch (_, stackTrace) {
+      return stackTrace;
+    }
+  }
+}