Disable mirrors metadata gen by default

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 dd05703ef06f82a1a89b64a5058d0fc18f876e07..22c2433f59d412ce7a549328ddbafdd74f710d09 100644
--- a/lib/src/compiler/compiler.dart
+++ b/lib/src/compiler/compiler.dart
@@ -184,7 +184,7 @@ class CompilerOptions {
       this.sourceMapComment: true,
       this.summarizeApi: true,
       this.unsafeForceCompile: false,
-      this.emitMetadata: true,
+      this.emitMetadata: false,
       this.closure: false,
       this.destructureNamedParams: false,
       this.moduleFormat: ModuleFormat.legacy});
@@ -217,7 +217,7 @@ class CompilerOptions {
         defaultsTo: 'legacy')
     ..addFlag('emit-metadata',
         help: 'emit metadata annotations queriable via mirrors',
-        defaultsTo: true)
+        defaultsTo: false)
     ..addFlag('closure-experimental',
         help: 'emit Closure Compiler-friendly code (experimental)',
         defaultsTo: false)