Provide option to suppress mirrors metadata

lib/src/compiler/compiler.dart

Index: lib/src/compiler/compiler.dart
diff --git a/lib/src/compiler/compiler.dart b/lib/src/compiler/compiler.dart
index 7f0db169609c93e60f713f00b0ddf50d5cac8030..81153ccba8f8572e806be003a276988d49a8804f 100644
--- a/lib/src/compiler/compiler.dart
+++ b/lib/src/compiler/compiler.dart
@@ -150,6 +150,9 @@ class CompilerOptions {
   /// This is required for a modular build process.
   final bool summarizeApi;
 
+  /// Whether to preserve metdata only accessible via mirrors
+  final bool preserveAnnotations;
+
   /// Whether to force compilation of code with static errors.
   final bool unsafeForceCompile;
 
@@ -181,6 +184,7 @@ class CompilerOptions {
       this.sourceMapComment: true,
       this.summarizeApi: true,
       this.unsafeForceCompile: false,
+      this.preserveAnnotations: false,
       this.closure: false,
       this.destructureNamedParams: false,
       this.moduleFormat: ModuleFormat.legacy});
@@ -190,6 +194,7 @@ class CompilerOptions {
         sourceMapComment = args['source-map-comment'],
         summarizeApi = args['summarize'],
         unsafeForceCompile = args['unsafe-force-compile'],
+        preserveAnnotations = args['preserve-annotations'],
         closure = args['closure-experimental'],
         destructureNamedParams = args['destructure-named-params'],
         moduleFormat = parseModuleFormat(args['modules']);
@@ -210,6 +215,9 @@ class CompilerOptions {
           'node': 'node.js modules (https://nodejs.org/api/modules.html)'
         },
         defaultsTo: 'legacy')
+    ..addFlag('preserve-annotations',

[Jennifer Messerly, 2016/05/17 21:39:42]

maybe "emit-metadata" -- slightly shorter?

we also seem to call it "metadata" in some of our docs:
https://www.dartlang.org/docs/dart-up-and-running/ch02.html#summary

(maybe it was to disambiguate "type annotations")

+        help: 'emit metadata annotations queriable via mirrors',
+        defaultsTo: false)
     ..addFlag('closure-experimental',
         help: 'emit Closure Compiler-friendly code (experimental)',
         defaultsTo: false)