Add associated binding set. Add associated_binding.html layout test.

mojo/public/js/bindings.js

Index: mojo/public/js/bindings.js
diff --git a/mojo/public/js/bindings.js b/mojo/public/js/bindings.js
index ed00554eb9a1036782443ef48b7b0f5e238436c4..7cc34500eac7860058bc908e426b988697bad84d 100644
--- a/mojo/public/js/bindings.js
+++ b/mojo/public/js/bindings.js
@@ -265,8 +265,8 @@ define("mojo/public/js/bindings", [
     this.bindingId_ = bindingId;
     this.binding_ = new Binding(interfaceType, impl, requestOrHandle);
 
-    this.binding_.setConnectionErrorHandler(function() {
-      this.bindingSet_.onConnectionError(bindingId);
+    this.binding_.setConnectionErrorHandler(function(reason) {
+      this.bindingSet_.onConnectionError(bindingId, reason);
     }.bind(this));
   }
 
@@ -303,11 +303,11 @@ define("mojo/public/js/bindings", [
     this.errorHandler_ = callback;
   };
 
-  BindingSet.prototype.onConnectionError = function(bindingId) {
+  BindingSet.prototype.onConnectionError = function(bindingId, reason) {
     this.bindings_.delete(bindingId);
 
     if (this.errorHandler_)
-      this.errorHandler_();
+      this.errorHandler_(reason);
   };
 
   var exports = {};