injectCode.js

function DOMtoString(document_root) {
	var html = '', node = document_root.firstChild;
	while (node) {
		switch (node.nodeType) {
			case Node.ELEMENT_NODE:
				html += node.outerHTML;
				break;
			case Node.TEXT_NODE:
				html += node.nodeValue;
				break;
			case Node.CDATA_SECTION_NODE:
				html += '<![CDATA[' + node.nodeValue + ']]>';
				break;
			case Node.COMMENT_NODE:
				html += '<!--' + node.nodeValue + '-->';
				break;
			case Node.DOCUMENT_TYPE_NODE:
				// (X)HTML documents are identified by public identifiers
				html += "<!DOCTYPE " + node.name + (node.publicId ? ' PUBLIC "' + node.publicId + '"' : '') + (!node.publicId && node.systemId ? ' SYSTEM' : '') + (node.systemId ? ' "' + node.systemId + '"' : '') + '>\n';
				break;
		}
		node = node.nextSibling;
	}
	return html;
}

// document.addEventListener("DOMContentLoaded", start, false)

window.onload=start()

function start() {
	chrome.extension.sendMessage({
		action : "getSource",
		source : DOMtoString(document)
	})
}