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

sdk/lib/debugger/debugger.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.
-
-/// Programmatically trigger breakpoints.
-library dart.debugger;
-
-/// Programmatically trigger breakpoints.
-class Debugger {
-  /// 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 static void breakHere();
-
-  /// If [expr] is true, stop the program as if a breakpoint where hit at the
-  /// following statement. See [breakHere].
-  external static void breakHereIf(bool expr);
-}