[DevTools] Extract part of DevTools into inspector app.

Source/devtools/front_end/platform/utilities.js

Index: Source/devtools/front_end/platform/utilities.js
diff --git a/Source/devtools/front_end/platform/utilities.js b/Source/devtools/front_end/platform/utilities.js
index 7c9301cf5abe8388163e879d5cef35f521994f35..45305c8b5905dcb8c15b43343a13b002a068d3ae 100644
--- a/Source/devtools/front_end/platform/utilities.js
+++ b/Source/devtools/front_end/platform/utilities.js
@@ -1435,3 +1435,24 @@ self.setImmediate = function(callback)
     Promise.resolve().then(callback).done();
     return 0;
 }
+
+/**
+ * @param {!function()} callback
+ * @suppressGlobalPropertiesCheck
+ */
+function runOnWindowLoad(callback)
+{
+    /**
+     * @suppressGlobalPropertiesCheck
+     */
+    function windowLoaded()
+    {
+        window.removeEventListener("DOMContentLoaded", windowLoaded, false);
+        callback();
+    }
+
+    if (document.readyState === "complete")
+        callback();
+    else
+        window.addEventListener("DOMContentLoaded", windowLoaded, false);
+}