Move registering of interceptors to the JsBackend.

lib/compiler/implementation/js_backend/backend.dart

Index: lib/compiler/implementation/js_backend/backend.dart
diff --git a/lib/compiler/implementation/js_backend/backend.dart b/lib/compiler/implementation/js_backend/backend.dart
index 120440ed1aa28adfe68ad16db3742819c877ba22..fe14f116855bd285c7467feddb8d543c7cb47eb4 100644
--- a/lib/compiler/implementation/js_backend/backend.dart
+++ b/lib/compiler/implementation/js_backend/backend.dart
@@ -661,6 +661,8 @@ class JavaScriptBackend extends Backend {
   ArgumentTypesRegistry argumentTypes;
   FieldTypesRegistry fieldTypes;
 
+  final Interceptors interceptors;
+
   List<CompilerTask> get tasks {
     return <CompilerTask>[builder, optimizer, generator, emitter];
   }
@@ -669,6 +671,7 @@ class JavaScriptBackend extends Backend {
       : namer = new Namer(compiler),
         returnInfo = new Map<Element, ReturnInfo>(),
         invalidateAfterCodegen = new List<Element>(),
+        interceptors = new Interceptors(compiler),
         super(compiler, constantSystem: JAVA_SCRIPT_CONSTANT_SYSTEM) {
     emitter = new CodeEmitterTask(compiler, namer, generateSourceMap);
     builder = new SsaBuilderTask(this);
@@ -686,6 +689,10 @@ class JavaScriptBackend extends Backend {
     return new JavaScriptItemCompilationContext();
   }
 
+  Element getInterceptor(Selector selector) {
+    return interceptors.getStaticInterceptorBySelector(selector);
+  }
+
   void enqueueHelpers(Enqueuer world) {
     enqueueAllTopLevelFunctions(compiler.jsHelperLibrary, world);