[Telemetry] Add script to snapshot page's HTML

telemetry/third_party/snap-it/content_script.js

Index: telemetry/third_party/snap-it/content_script.js
diff --git a/telemetry/third_party/snap-it/content_script.js b/telemetry/third_party/snap-it/content_script.js
new file mode 100644
index 0000000000000000000000000000000000000000..1abfc1f5bcf61c6adeda10a6df6d49a81b763420
--- /dev/null
+++ b/telemetry/third_party/snap-it/content_script.js
@@ -0,0 +1,31 @@
+/**
+ * Send the neccessary HTMLSerializer properties back to the extension.
+ *
+ * @param {HTMLSerializer} htmlSerializer The HTMLSerializer.
+ */
+function sendHTMLSerializerToExtension(htmlSerializer) {
+  var result = {
+    'html': htmlSerializer.html,
+    'frameHoles': htmlSerializer.frameHoles,
+    'idToStyleIndex': htmlSerializer.idToStyleIndex,
+    'idToStyleMap': htmlSerializer.idToStyleMap,
+    'windowHeight': htmlSerializer.windowHeight,
+    'windowWidth': htmlSerializer.windowWidth,
+    'rootId': htmlSerializer.rootId,
+    'rootStyleIndex': htmlSerializer.rootStyleIndex,
+    'pseudoElementSelectorToCSSMap':
+        htmlSerializer.pseudoElementSelectorToCSSMap,
+    'pseudoElementPlaceHolderIndex':
+        htmlSerializer.pseudoElementPlaceHolderIndex,
+    'pseudoElementTestingStyleIndex':
+        htmlSerializer.pseudoElementStyleTestingIndex,
+    'pseudoElementTestingStyleId': htmlSerializer.pseudoElementTestingStyleId,
+    'unusedId': htmlSerializer.generateId(document),
+    'frameIndex': htmlSerializer.iframeFullyQualifiedName(window)
+  };
+  chrome.runtime.sendMessage(result);
+}
+
+var htmlSerializer = new HTMLSerializer();
+htmlSerializer.processDocument(document);
+htmlSerializer.fillHolesAsync(document, sendHTMLSerializerToExtension);