[fasta] Flip source flag and include source by default

pkg/front_end/lib/src/fasta/compiler_command_line.dart

 // Copyright (c) 2016, 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.
 
 library fasta.compiler_command_line;
 
 import 'dart:io' show exit;
 
 import 'command_line.dart' show CommandLine, argumentError;
 
@@ skipping 14 matching lines @@
   CompilerCommandLine(String programName, List<String> arguments)
       : programName = programName,
         super(arguments,
             specification: optionSpecification,
             usage: computeUsage(programName, false));
 
   bool get verify => options.containsKey("--verify");
 
   bool get dumpIr => options.containsKey("--dump-ir");
 
-  bool get includeSource => options.containsKey("--include-source");
+  bool get excludeSource => options.containsKey("--exclude-source");
 
   bool get help {
     return options.containsKey("--help") ||
         options.containsKey("-h") ||
         options.containsKey("/h") ||
         options.containsKey("/?");
   }
 
   void validate() {
     if (help) {
@@ skipping 116 matching lines @@
     Read the SDK platform from <file>, which should be in Dill/Kernel IR format
     and contain the Dart SDK.
 
   --verify
     Check that the generated output is free of various problems. This is mostly
     useful for developers of this compiler or Kernel transformations.
 
   --dump-ir
     Print compiled libraries in Kernel source notation.
 
-  --include-source
-    Include source code in the dill file. Used for debugging.
+  --exclude-source
+    Do not include source code in the dill file.
 
   --compile-sdk=<patched_sdk>
     Compile the SDK from scratch instead of reading it from 'platform.dill'.
 
   --fatal=errors
   --fatal=warnings
   --fatal=nits
     Makes messages of the given kinds fatal, that is, immediately stop the
     compiler with a non-zero exit-code. In --verbose mode, also display an
     internal stack trace from the compiler. Multiple kinds can be separated by
     commas, for example, --fatal=errors,warnings.
 """;