DevTools: use setImmediate instead of setTimeout for dispatching messages on devtools frontend in d…

Source/devtools/front_end/externs.js

Index: Source/devtools/front_end/externs.js
diff --git a/Source/devtools/front_end/externs.js b/Source/devtools/front_end/externs.js
index becf909d0e83765eba050600790379e77fecda02..d0c9a07520d47f9d0eaab0315716bc721eb77037 100644
--- a/Source/devtools/front_end/externs.js
+++ b/Source/devtools/front_end/externs.js
@@ -30,6 +30,12 @@
 
 // WebKit Web Facing API
 
+/**
+ * @param {!Object} object
+ * @param {!Function} callback
+ */
+Object.observe = function(object, callback) {}
+
 /** @type {boolean} */
 Event.prototype.isMetaOrCtrlForTest;