Rename 'dart:debugger' to 'dart:developer'

sdk/lib/developer/developer.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// ## Status: Unstable
+///
+/// The dart:dev library is unstable and its API might change slightly as a
+/// result of developer feedback. This library is platform dependent and
+/// therefore it has implementations for both dart2js and the Dart VM. Both are
+/// under development and may not support all operations yet.
+///
+///
+library dart.dev;
+
+/// Stop the program as if a breakpoint where hit at the following statement.
+/// NOTE: When invoked, the isolate will not return until a debugger
+/// continues execution. When running in the Dart VM the behaviour is the same
+/// regardless of whether or not a debugger is connected. When compiled to
+/// JavaScript, this uses the "debugger" statement, and behaves exactly as
+/// that does.
+external void breakHere();
+
+/// If [expr] is true, stop the program as if a breakpoint where hit at the
+/// following statement. See [breakHere].
+external void breakHereIf(bool expr);