DevTools: Prevent setting huge textContent in UI.

Source/devtools/front_end/DOMExtension.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 552 matching lines @@
         return null;
     var node = this.previousSibling;
     while (node && node.lastChild)
         node = node.lastChild;
     if (node)
         return node;
     return this.parentNode;
 }
 
 /**
+ * @param {*} text
+ * @param {string=} placeholder
+ * @return {boolean} true if was truncated
+ */
+Node.prototype.setTextContentTruncatedIfNeeded = function(text, placeholder)
+{
+    // Huge texts in the UI reduce rendering performance drastically.
+    // Moreover, Blink/WebKit uses <unsigned short> internally for storing text content
+    // length, so texts longer than 65535 are inherently displayed incorrectly.
+    const maxTextContentLength = 65535;
+
+    if (typeof text === "string" && text.length > maxTextContentLength) {
+        this.textContent = typeof placeholder === "string" ? placeholder : text.trimEnd(maxTextContentLength);
+        return true;
+    }
+
+    this.textContent = text;
+    return false;
+}
+
+/**
  * @return {boolean}
  */
 function isEnterKey(event) {
     // Check if in IME.
     return event.keyCode !== 229 && event.keyIdentifier === "Enter";
 }
 
 function consumeEvent(e)
 {
     e.consume();
 }