Fix a batch of DDC SDK compile errors.

pkg/dev_compiler/tool/input_sdk/private/annotations.dart

Index: pkg/dev_compiler/tool/input_sdk/private/annotations.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/annotations.dart b/pkg/dev_compiler/tool/input_sdk/private/annotations.dart
index b7cc970ace3e42e3478ed72880e7959d125656ff..2e52c82508ee3d990a77a20240f9fff7f9afd18d 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/annotations.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/annotations.dart
@@ -4,6 +4,11 @@
 
 part of dart._js_helper;
 
+/// Tells the optimizing compiler to always inline the annotated method.
+class ForceInline {
+  const ForceInline();
+}
+
 /// Tells the optimizing compiler that the annotated method cannot throw.
 /// Requires @NoInline() to function correctly.
 class NoThrows {