[Telemetry] Add script to snapshot page's HTML

telemetry/third_party/snap-it/popup.js

Index: telemetry/third_party/snap-it/popup.js
diff --git a/telemetry/third_party/snap-it/popup.js b/telemetry/third_party/snap-it/popup.js
new file mode 100644
index 0000000000000000000000000000000000000000..17a92234ae74ca48479c9c83f36b85b7e40103e9
--- /dev/null
+++ b/telemetry/third_party/snap-it/popup.js
@@ -0,0 +1,340 @@
+document.addEventListener('DOMContentLoaded', function() {
+  if (document.getElementById('button')) {
+    document.getElementById('button').addEventListener('click', click);
+  }
+});
+
+function click() {
+  var messages = []
+  var results;
+  chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
+    messages.push(message);
+    if (results && messages.length == results.length) {
+      completeProcess(messages);
+    }
+  });
+
+  var serializer = {file: 'HTMLSerializer.js', allFrames: true};
+  chrome.tabs.executeScript(null, serializer, function() {
+    var contentScript = {file: 'content_script.js', allFrames: true};
+    chrome.tabs.executeScript(null, contentScript, function(response) {
+      results = response;
+      if (messages.length == results.length)
+        completeProcess(messages);
+    });
+  });
+
+  var a = document.getElementById('button');
+  a.className = 'serialize';
+  a.innerHTML = 'Serializing...';
+  a.removeEventListener('click', click);
+}
+
+/**
+ * Takes all the responses from the injected content scripts and creates the
+ * HTML file for download.
+ * 
+ * @param {Array<Object>} messages The response from all of the injected content
+ *     scripts.
+ */
+function completeProcess(messages) {
+  var html = outputHTMLString(messages);
+  var file = new Blob([html], {type: 'text/html'});
+  var url = URL.createObjectURL(file);
+
+  var a = document.getElementById('button');
+  a.className = 'download';
+  a.innerHTML = 'Download';
+  a.href = url;
+  a.download = "snap-it.html";
+}
+
+/**
+ * Converts the responses from the injected content scripts into a string
+ * representing the HTML.
+ * 
+ * @param {Array<Object>} messages The response from all of the injected content
+ *     scripts.
+ * @return {string} The resulting HTML.
+ */
+function outputHTMLString(messages) {
+  var rootIndex = 0;
+  for (var i = 1; i < messages.length; i++) {
+    rootIndex = messages[i].frameIndex === '0' ? i : rootIndex;
+  }
+  fillRemainingHolesAndMinimizeStyles(messages, rootIndex);
+  return messages[rootIndex].html.join('');
+}
+
+/**
+ * Fills all of the gaps in |messages[i].html|.
+ *
+ * @param {Array<Object>} messages The response from all of the injected content
+ *     scripts.
+ * @param {number} i The index of messages to use.
+ */
+function fillRemainingHolesAndMinimizeStyles(messages, i) {
+  var html = messages[i].html;
+  var frameHoles = messages[i].frameHoles;
+  for (var index in frameHoles) {
+    if (frameHoles.hasOwnProperty(index)) {
+      var frameIndex = frameHoles[index];
+      for (var j = 0; j < messages.length; j++) {
+        if (messages[j].frameIndex == frameIndex) {
+          fillRemainingHolesAndMinimizeStyles(messages, j);
+          html[index] = messages[j].html.join('');
+        }
+      }
+    }
+  }
+  minimizeStyles(messages[i]);
+}
+
+/**
+ * Removes all style attribute properties that are unneeded.
+ *
+ * @param {Object} message The message Object whose style attributes should be
+ *     minimized.
+ */
+function minimizeStyles(message) {
+  var nestingDepth = message.frameIndex.split('.').length - 1;
+  var iframe = document.createElement('iframe');
+  document.body.appendChild(iframe);
+  iframe.setAttribute(
+      'style',
+      `height: ${message.windowHeight}px;` + 
+      `width: ${message.windowWidth}px;`);
+
+  var html = message.html.join('');
+  html = unescapeHTML(html, nestingDepth);
+  iframe.contentDocument.documentElement.innerHTML = html;
+  var doc = iframe.contentDocument;
+
+  // Remove entry in |message.html| where extra style element was specified.
+  message.html[message.pseudoElementTestingStyleIndex] = '';
+  var finalPseudoElements = [];
+  for (var selector in message.pseudoElementSelectorToCSSMap) {
+    minimizePseudoElementStyle(message, doc, selector, finalPseudoElements);
+  }
+
+  message.html[message.pseudoElementPlaceHolderIndex] =
+      `<style>${finalPseudoElements.join(' ')}</style>`;
+
+  if (message.rootStyleIndex) {
+    minimizeStyle(
+        message,
+        doc,
+        doc.documentElement,
+        message.rootId,
+        message.rootStyleIndex);
+  }
+
+  for (var id in message.idToStyleIndex) {
+    var index = message.idToStyleIndex[id];
+    var element = doc.getElementById(id);
+    if (element) {
+      minimizeStyle(message, doc, element, id, index);
+    }
+  }
+  iframe.remove();
+}
+
+/**
+ * Removes all style attribute properties that are unneeded for a single
+ *     pseudo element.
+ *
+ * @param {Object} message The message Object that contains the pseudo element
+ *     whose style attributes should be minimized.
+ * @param {Document} doc The Document that contains the rendered HTML.
+ * @param {string} selector The CSS selector for the pseudo element.
+ * @param {Array<string>} finalPseudoElements An array to contain the final
+ *     declaration of pseudo elements.  It will be updated to reflect the pseudo
+ *     element that is being processed.
+ */
+function minimizePseudoElementStyle(
+    message,
+    doc,
+    selector,
+    finalPseudoElements) {
+  var maxNumberOfIterations = 5;
+  var match = selector.match(/^#(.*):(:.*)$/);
+  var id = match[1];
+  var type = match[2];
+  var element = doc.getElementById(id);
+  if (element) {
+    var originalStyleMap = message.pseudoElementSelectorToCSSMap[selector];
+    var requiredStyleMap = {};
+    // We compare the computed style before and after removing the pseudo
+    // element and accumulate the differences in |requiredStyleMap|. The pseudo
+    // element is removed by changing the element id. Because some properties
+    // affect other properties, such as border-style: solid causing a change in
+    // border-width, we do this iteratively until a fixed-point is reached (or
+    // |maxNumberOfIterations| is hit).
+    // TODO(sfine): Unify this logic with minimizeStyles.
+    for (var i = 0; i < maxNumberOfIterations; i++) {
+      var currentPseudoElement = ['#' + message.unusedId + ':' + type + '{'];
+      currentPseudoElement.push(buildStyleAttribute(requiredStyleMap));
+      currentPseudoElement.push('}');
+      element.setAttribute('id', message.unusedId);
+      var style = doc.getElementById(message.pseudoElementTestingStyleId);
+      style.innerHTML = currentPseudoElement.join(' ');
+      var foundNewRequiredStyle = updateMinimizedStyleMap(
+          doc,
+          element,
+          originalStyleMap,
+          requiredStyleMap,
+          type);
+      if (!foundNewRequiredStyle) {
+        break;
+      }
+    }
+    element.setAttribute('id', id);
+    finalPseudoElements.push('#' + id + ':' + type + '{');
+    var finalPseudoElement = buildStyleAttribute(requiredStyleMap);
+    var nestingDepth = message.frameIndex.split('.').length - 1;
+    finalPseudoElement = finalPseudoElement.replace(
+        /"/g,
+        escapedQuote(nestingDepth));
+    finalPseudoElements.push(finalPseudoElement);
+    finalPseudoElements.push('}');
+  }
+}
+
+
+/**
+ * Removes all style attribute properties that are unneeded for a single
+ *     element.
+ *
+ * @param {Object} message The message Object that contains the element whose
+ *     style attributes should be minimized.
+ * @param {Document} doc The Document that contains the rendered HTML.
+ * @param {Element} element The Element whose style attributes should be
+ *     minimized.
+ * @param {string} id The id of the Element in the final page.
+ * @param {number} index The index in |message.html| where the Element's style
+ *     attribute is specified.
+ */
+function minimizeStyle(message, doc, element, id, index) {
+  var originalStyleAttribute = element.getAttribute('style');
+  var originalStyleMap = message.idToStyleMap[id];
+  var requiredStyleMap = {};
+  var maxNumberOfIterations = 5;
+
+  // We compare the computed style before and after removing the style attribute
+  // and accumulate the differences in |requiredStyleMap|. Because some
+  // properties affect other properties, such as boder-style: solid causing a
+  // change in border-width, we do this iteratively until a fixed-point is
+  // reached (or |maxNumberOfIterations| is hit).
+  for (var i = 0; i < maxNumberOfIterations; i++) {
+    element.setAttribute('style', buildStyleAttribute(requiredStyleMap));
+    var foundNewRequiredStyle = updateMinimizedStyleMap(
+        doc,
+        element,
+        originalStyleMap,
+        requiredStyleMap,
+        null);
+    element.setAttribute('style', buildStyleAttribute(originalStyleMap));
+    if (!foundNewRequiredStyle) {
+      break;
+    }
+  }
+
+  var finalStyleAttribute = buildStyleAttribute(requiredStyleMap);
+  if (finalStyleAttribute) {
+    var nestingDepth = message.frameIndex.split('.').length - 1;
+    finalStyleAttribute = finalStyleAttribute.replace(
+        /"/g,
+        escapedQuote(nestingDepth + 1));
+    var quote = escapedQuote(nestingDepth);
+    message.html[index] = `style=${quote}${finalStyleAttribute}${quote} `;
+  } else {
+    message.html[index] = '';
+  }
+}
+
+/**
+ * We compare the original computed style with the minimized computed style
+ * and update |minimizedStyleMap| based on any differences.
+ *
+ * @param {Document} doc The Document that contains the rendered HTML.
+ * @param {Element} element The Element whose style attributes should be
+ *     minimized.
+ * @param {Object<string, string>} originalStyleMap A map representing the
+ *     original computed style values. The keys are style attribute property
+ *     names. The values are the corresponding property values.
+ * @param {Object<string, string>} minimizedStyleMap A map representing the
+ *     minimized style values. The keys are style attribute property names. The
+ *     values are the corresponding property values.
+ * @param {string} pseudo If the style describes an ordinary
+ *     Element, then |pseudo| will be set to null.  If the style describes a
+ *     pseudo element, then |pseudo| will be the string that represents that
+ *     pseudo element.
+ * @return {boolean} Returns true if minimizedStyleMap was changed. Returns false
+ *     otherwise.
+ */
+function updateMinimizedStyleMap(
+    doc,
+    element,
+    originalStyleMap,
+    minimizedStyleMap,
+    pseudo) {
+  var currentComputedStyle = doc.defaultView.getComputedStyle(element, pseudo);
+  var foundNewRequiredStyle = false;
+  for (var property in originalStyleMap) {
+    var originalValue = originalStyleMap[property];
+    if (originalValue != currentComputedStyle.getPropertyValue(property)) {
+      minimizedStyleMap[property] = originalValue;
+      foundNewRequiredStyle = true;
+    }
+  }
+  return foundNewRequiredStyle;
+}
+
+/**
+ * Build a style attribute from a map of property names to property values.
+ *
+ * @param {Object<string, string} styleMap The keys are style attribute property
+ *     names. The values are the corresponding property values.
+ * @return {string} The correct style attribute.
+ */
+function buildStyleAttribute(styleMap) {
+  var styleAttribute = [];
+  for (var property in styleMap) {
+    styleAttribute.push(property + ': ' + styleMap[property] + ';');
+  }
+  return styleAttribute.join(' ');
+}
+
+/**
+ * Take a string that represents valid HTML and unescape it so that it can be
+ * rendered.
+ *
+ * @param {string} html The HTML to unescape.
+ * @param {number} nestingDepth The number of times the HTML must be unescaped.
+ * @return {string} The unescaped HTML.
+ */
+function unescapeHTML(html, nestingDepth) {
+  var div = document.createElement('div');
+  for (var i = 0; i < nestingDepth; i++) {
+    div.innerHTML = `<iframe srcdoc="${html}"></iframe>`;
+    html = div.childNodes[0].attributes.srcdoc.value;
+  }
+  return html;
+}
+
+/**
+ * Calculate the correct encoding of a quotation mark that should be used given
+ * the nesting depth of the window in the frame tree.
+ *
+ * @param {number} depth The nesting depth of the appropriate window in the
+ *     frame tree.
+ * @return {string} The correctly escaped string. 
+ */
+function escapedQuote(depth) {
+  if (depth == 0) {
+    return '"';
+  } else {
+    var arr = 'amp;'.repeat(depth-1);
+    return '&' + arr + 'quot;';
+  }
+}