Document --analyze-all option.

dart/sdk/lib/_internal/compiler/implementation/dart2js.dart

 // Copyright (c) 2012, 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 dart2js;
 
 import 'dart:io';
 import 'dart:uri';
 import 'dart:utf';
 
@@ skipping 357 matching lines @@
 
   -h, /h, /?, --help
     Display this message (add -v for information about all options).
 
   -v, --verbose
     Display verbose information.
 
   -p<path>, --package-root=<path>
     Where to find packages, that is, "package:..." imports.
 
+  --analyze-all
+    Analyze all code.  Without this option, the compiler only analyzes
+    code that is reachable from [main].  This option is useful for
+    finding errors in libraries, but using it can result in bigger and
+    slower output.
+
   --minify
     Generate minified output.
 
   --suppress-warnings
     Do not display any warnings.
 
   --enable-diagnostic-colors
     Add colors to diagnostic messages.
 
 The following options are only used for compiler development and may
@@ skipping 46 matching lines @@
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }