Add --no-declaration-casts option to analyzer.

pkg/analyzer/lib/src/task/options.dart

Index: pkg/analyzer/lib/src/task/options.dart
diff --git a/pkg/analyzer/lib/src/task/options.dart b/pkg/analyzer/lib/src/task/options.dart
index c761f7680bfe7c4ce9771b4fb084ca9be27293fd..ccae7d61a3b80958d74e322a0c40611bebf580ee 100644
--- a/pkg/analyzer/lib/src/task/options.dart
+++ b/pkg/analyzer/lib/src/task/options.dart
@@ -58,6 +58,7 @@ class AnalyzerOptions {
   static const String strong_mode = 'strong-mode';
 
   // Strong mode options, see AnalysisOptionsImpl for documentation.
+  static const String declarationCasts = 'declaration-casts';
   static const String implicitCasts = 'implicit-casts';
   static const String implicitDynamic = 'implicit-dynamic';
 
@@ -573,6 +574,9 @@ class _OptionsProcessor {
       AnalysisOptionsImpl options, Object feature, Object value) {
     bool boolValue = toBool(value);
     if (boolValue != null) {
+      if (feature == AnalyzerOptions.declarationCasts) {
+        options.declarationCasts = boolValue;
+      }
       if (feature == AnalyzerOptions.implicitCasts) {
         options.implicitCasts = boolValue;
       }