Added 'dynamic' keyword, so that 'Dynamic' can be deprecated.

lib/compiler/implementation/dart_backend/placeholder_collector.dart

Index: lib/compiler/implementation/dart_backend/placeholder_collector.dart
diff --git a/lib/compiler/implementation/dart_backend/placeholder_collector.dart b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
index 98e564d077076db2b8de2173335a46fe51362a0f..3026e7a16d317e9ab26517f74048ebe0f5bab232 100644
--- a/lib/compiler/implementation/dart_backend/placeholder_collector.dart
+++ b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
@@ -415,7 +415,8 @@ class PlaceholderCollector extends AbstractVisitor {
   static bool isDynamicType(TypeAnnotation typeAnnotation) {
     if (!isPlainTypeName(typeAnnotation)) return false;
     String name = typeAnnotation.typeName.asIdentifier().source.slowToString();
-    return name == 'Dynamic';
+    // TODO(aprelev@gmail.com): Removed deprecated Dynamic keyword support.
+    return name == 'Dynamic' || name == 'dynamic';
   }
 
   visitTypeAnnotation(TypeAnnotation node) {