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third_party/google_input_tools/third_party/closure_library/closure/goog/html/safehtml.js

Index: third_party/google_input_tools/third_party/closure_library/closure/goog/html/safehtml.js
diff --git a/third_party/google_input_tools/third_party/closure_library/closure/goog/html/safehtml.js b/third_party/google_input_tools/third_party/closure_library/closure/goog/html/safehtml.js
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+// Copyright 2013 The Closure Library Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS-IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+
+/**
+ * @fileoverview The SafeHtml type and its builders.
+ *
+ * TODO(xtof): Link to document stating type contract.
+ */
+
+goog.provide('goog.html.SafeHtml');
+
+goog.require('goog.array');
+goog.require('goog.asserts');
+goog.require('goog.dom.TagName');
+goog.require('goog.dom.tags');
+goog.require('goog.html.SafeStyle');
+goog.require('goog.html.SafeStyleSheet');
+goog.require('goog.html.SafeUrl');
+goog.require('goog.html.TrustedResourceUrl');
+goog.require('goog.i18n.bidi.Dir');
+goog.require('goog.i18n.bidi.DirectionalString');
+goog.require('goog.object');
+goog.require('goog.string');
+goog.require('goog.string.Const');
+goog.require('goog.string.TypedString');
+
+
+
+/**
+ * A string that is safe to use in HTML context in DOM APIs and HTML documents.
+ *
+ * A SafeHtml is a string-like object that carries the security type contract
+ * that its value as a string will not cause untrusted script execution when
+ * evaluated as HTML in a browser.
+ *
+ * Values of this type are guaranteed to be safe to use in HTML contexts,
+ * such as, assignment to the innerHTML DOM property, or interpolation into
+ * a HTML template in HTML PC_DATA context, in the sense that the use will not
+ * result in a Cross-Site-Scripting vulnerability.
+ *
+ * Instances of this type must be created via the factory methods
+ * ({@code goog.html.SafeHtml.create}, {@code goog.html.SafeHtml.htmlEscape}),
+ * etc and not by invoking its constructor.  The constructor intentionally
+ * takes no parameters and the type is immutable; hence only a default instance
+ * corresponding to the empty string can be obtained via constructor invocation.
+ *
+ * @see goog.html.SafeHtml#create
+ * @see goog.html.SafeHtml#htmlEscape
+ * @constructor
+ * @final
+ * @struct
+ * @implements {goog.i18n.bidi.DirectionalString}
+ * @implements {goog.string.TypedString}
+ */
+goog.html.SafeHtml = function() {
+  /**
+   * The contained value of this SafeHtml.  The field has a purposely ugly
+   * name to make (non-compiled) code that attempts to directly access this
+   * field stand out.
+   * @private {string}
+   */
+  this.privateDoNotAccessOrElseSafeHtmlWrappedValue_ = '';
+
+  /**
+   * A type marker used to implement additional run-time type checking.
+   * @see goog.html.SafeHtml#unwrap
+   * @const
+   * @private
+   */
+  this.SAFE_HTML_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ =
+      goog.html.SafeHtml.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_;
+
+  /**
+   * This SafeHtml's directionality, or null if unknown.
+   * @private {?goog.i18n.bidi.Dir}
+   */
+  this.dir_ = null;
+};
+
+
+/**
+ * @override
+ * @const
+ */
+goog.html.SafeHtml.prototype.implementsGoogI18nBidiDirectionalString = true;
+
+
+/** @override */
+goog.html.SafeHtml.prototype.getDirection = function() {
+  return this.dir_;
+};
+
+
+/**
+ * @override
+ * @const
+ */
+goog.html.SafeHtml.prototype.implementsGoogStringTypedString = true;
+
+
+/**
+ * Returns this SafeHtml's value a string.
+ *
+ * IMPORTANT: In code where it is security relevant that an object's type is
+ * indeed {@code SafeHtml}, use {@code goog.html.SafeHtml.unwrap} instead of
+ * this method. If in doubt, assume that it's security relevant. In particular,
+ * note that goog.html functions which return a goog.html type do not guarantee
+ * that the returned instance is of the right type. For example:
+ *
+ * <pre>
+ * var fakeSafeHtml = new String('fake');
+ * fakeSafeHtml.__proto__ = goog.html.SafeHtml.prototype;
+ * var newSafeHtml = goog.html.SafeHtml.htmlEscape(fakeSafeHtml);
+ * // newSafeHtml is just an alias for fakeSafeHtml, it's passed through by
+ * // goog.html.SafeHtml.htmlEscape() as fakeSafeHtml
+ * // instanceof goog.html.SafeHtml.
+ * </pre>
+ *
+ * @see goog.html.SafeHtml#unwrap
+ * @override
+ */
+goog.html.SafeHtml.prototype.getTypedStringValue = function() {
+  return this.privateDoNotAccessOrElseSafeHtmlWrappedValue_;
+};
+
+
+if (goog.DEBUG) {
+  /**
+   * Returns a debug string-representation of this value.
+   *
+   * To obtain the actual string value wrapped in a SafeHtml, use
+   * {@code goog.html.SafeHtml.unwrap}.
+   *
+   * @see goog.html.SafeHtml#unwrap
+   * @override
+   */
+  goog.html.SafeHtml.prototype.toString = function() {
+    return 'SafeHtml{' + this.privateDoNotAccessOrElseSafeHtmlWrappedValue_ +
+        '}';
+  };
+}
+
+
+/**
+ * Performs a runtime check that the provided object is indeed a SafeHtml
+ * object, and returns its value.
+ * @param {!goog.html.SafeHtml} safeHtml The object to extract from.
+ * @return {string} The SafeHtml object's contained string, unless the run-time
+ *     type check fails. In that case, {@code unwrap} returns an innocuous
+ *     string, or, if assertions are enabled, throws
+ *     {@code goog.asserts.AssertionError}.
+ */
+goog.html.SafeHtml.unwrap = function(safeHtml) {
+  // Perform additional run-time type-checking to ensure that safeHtml is indeed
+  // an instance of the expected type.  This provides some additional protection
+  // against security bugs due to application code that disables type checks.
+  // Specifically, the following checks are performed:
+  // 1. The object is an instance of the expected type.
+  // 2. The object is not an instance of a subclass.
+  // 3. The object carries a type marker for the expected type. "Faking" an
+  // object requires a reference to the type marker, which has names intended
+  // to stand out in code reviews.
+  if (safeHtml instanceof goog.html.SafeHtml &&
+      safeHtml.constructor === goog.html.SafeHtml &&
+      safeHtml.SAFE_HTML_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ ===
+          goog.html.SafeHtml.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_) {
+    return safeHtml.privateDoNotAccessOrElseSafeHtmlWrappedValue_;
+  } else {
+    goog.asserts.fail('expected object of type SafeHtml, got \'' +
+                      safeHtml + '\'');
+    return 'type_error:SafeHtml';
+  }
+};
+
+
+/**
+ * Shorthand for union of types that can sensibly be converted to strings
+ * or might already be SafeHtml (as SafeHtml is a goog.string.TypedString).
+ * @private
+ * @typedef {string|number|boolean|!goog.string.TypedString|
+ *           !goog.i18n.bidi.DirectionalString}
+ */
+goog.html.SafeHtml.TextOrHtml_;
+
+
+/**
+ * Returns HTML-escaped text as a SafeHtml object.
+ *
+ * If text is of a type that implements
+ * {@code goog.i18n.bidi.DirectionalString}, the directionality of the new
+ * {@code SafeHtml} object is set to {@code text}'s directionality, if known.
+ * Otherwise, the directionality of the resulting SafeHtml is unknown (i.e.,
+ * {@code null}).
+ *
+ * @param {!goog.html.SafeHtml.TextOrHtml_} textOrHtml The text to escape. If
+ *     the parameter is of type SafeHtml it is returned directly (no escaping
+ *     is done).
+ * @return {!goog.html.SafeHtml} The escaped text, wrapped as a SafeHtml.
+ */
+goog.html.SafeHtml.htmlEscape = function(textOrHtml) {
+  if (textOrHtml instanceof goog.html.SafeHtml) {
+    return textOrHtml;
+  }
+  var dir = null;
+  if (textOrHtml.implementsGoogI18nBidiDirectionalString) {
+    dir = textOrHtml.getDirection();
+  }
+  var textAsString;
+  if (textOrHtml.implementsGoogStringTypedString) {
+    textAsString = textOrHtml.getTypedStringValue();
+  } else {
+    textAsString = String(textOrHtml);
+  }
+  return goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+      goog.string.htmlEscape(textAsString), dir);
+};
+
+
+/**
+ * Returns HTML-escaped text as a SafeHtml object, with newlines changed to
+ * &lt;br&gt;.
+ * @param {!goog.html.SafeHtml.TextOrHtml_} textOrHtml The text to escape. If
+ *     the parameter is of type SafeHtml it is returned directly (no escaping
+ *     is done).
+ * @return {!goog.html.SafeHtml} The escaped text, wrapped as a SafeHtml.
+ */
+goog.html.SafeHtml.htmlEscapePreservingNewlines = function(textOrHtml) {
+  if (textOrHtml instanceof goog.html.SafeHtml) {
+    return textOrHtml;
+  }
+  var html = goog.html.SafeHtml.htmlEscape(textOrHtml);
+  return goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+      goog.string.newLineToBr(goog.html.SafeHtml.unwrap(html)),
+      html.getDirection());
+};
+
+
+/**
+ * Returns HTML-escaped text as a SafeHtml object, with newlines changed to
+ * &lt;br&gt; and escaping whitespace to preserve spatial formatting. Character
+ * entity #160 is used to make it safer for XML.
+ * @param {!goog.html.SafeHtml.TextOrHtml_} textOrHtml The text to escape. If
+ *     the parameter is of type SafeHtml it is returned directly (no escaping
+ *     is done).
+ * @return {!goog.html.SafeHtml} The escaped text, wrapped as a SafeHtml.
+ */
+goog.html.SafeHtml.htmlEscapePreservingNewlinesAndSpaces = function(
+    textOrHtml) {
+  if (textOrHtml instanceof goog.html.SafeHtml) {
+    return textOrHtml;
+  }
+  var html = goog.html.SafeHtml.htmlEscape(textOrHtml);
+  return goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+      goog.string.whitespaceEscape(goog.html.SafeHtml.unwrap(html)),
+      html.getDirection());
+};
+
+
+/**
+ * Coerces an arbitrary object into a SafeHtml object.
+ *
+ * If {@code textOrHtml} is already of type {@code goog.html.SafeHtml}, the same
+ * object is returned. Otherwise, {@code textOrHtml} is coerced to string, and
+ * HTML-escaped. If {@code textOrHtml} is of a type that implements
+ * {@code goog.i18n.bidi.DirectionalString}, its directionality, if known, is
+ * preserved.
+ *
+ * @param {!goog.html.SafeHtml.TextOrHtml_} textOrHtml The text or SafeHtml to
+ *     coerce.
+ * @return {!goog.html.SafeHtml} The resulting SafeHtml object.
+ * @deprecated Use goog.html.SafeHtml.htmlEscape.
+ */
+goog.html.SafeHtml.from = goog.html.SafeHtml.htmlEscape;
+
+
+/**
+ * @const
+ * @private
+ */
+goog.html.SafeHtml.VALID_NAMES_IN_TAG_ = /^[a-zA-Z0-9-]+$/;
+
+
+/**
+ * Set of attributes containing URL as defined at
+ * http://www.w3.org/TR/html5/index.html#attributes-1.
+ * @private @const {!Object<string,boolean>}
+ */
+goog.html.SafeHtml.URL_ATTRIBUTES_ = goog.object.createSet('action', 'cite',
+    'data', 'formaction', 'href', 'manifest', 'poster', 'src');
+
+
+/**
+ * Tags which are unsupported via create(). They might be supported via a
+ * tag-specific create method. These are tags which might require a
+ * TrustedResourceUrl in one of their attributes or a restricted type for
+ * their content.
+ * @private @const {!Object<string,boolean>}
+ */
+goog.html.SafeHtml.NOT_ALLOWED_TAG_NAMES_ = goog.object.createSet(
+    goog.dom.TagName.EMBED, goog.dom.TagName.IFRAME, goog.dom.TagName.LINK,
+    goog.dom.TagName.OBJECT, goog.dom.TagName.SCRIPT, goog.dom.TagName.STYLE,
+    goog.dom.TagName.TEMPLATE);
+
+
+/**
+ * @typedef {string|number|goog.string.TypedString|
+ *     goog.html.SafeStyle.PropertyMap}
+ * @private
+ */
+goog.html.SafeHtml.AttributeValue_;
+
+
+/**
+ * Creates a SafeHtml content consisting of a tag with optional attributes and
+ * optional content.
+ *
+ * For convenience tag names and attribute names are accepted as regular
+ * strings, instead of goog.string.Const. Nevertheless, you should not pass
+ * user-controlled values to these parameters. Note that these parameters are
+ * syntactically validated at runtime, and invalid values will result in
+ * an exception.
+ *
+ * Example usage:
+ *
+ * goog.html.SafeHtml.create('br');
+ * goog.html.SafeHtml.create('div', {'class': 'a'});
+ * goog.html.SafeHtml.create('p', {}, 'a');
+ * goog.html.SafeHtml.create('p', {}, goog.html.SafeHtml.create('br'));
+ *
+ * goog.html.SafeHtml.create('span', {
+ *   'style': {'margin': '0'}
+ * });
+ *
+ * To guarantee SafeHtml's type contract is upheld there are restrictions on
+ * attribute values and tag names.
+ *
+ * - For attributes which contain script code (on*), a goog.string.Const is
+ *   required.
+ * - For attributes which contain style (style), a goog.html.SafeStyle or a
+ *   goog.html.SafeStyle.PropertyMap is required.
+ * - For attributes which are interpreted as URLs (e.g. src, href) a
+ *   goog.html.SafeUrl, goog.string.Const or string is required. If a string
+ *   is passed, it will be sanitized with SafeUrl.sanitize().
+ * - For tags which can load code, more specific goog.html.SafeHtml.create*()
+ *   functions must be used. Tags which can load code and are not supported by
+ *   this function are embed, iframe, link, object, script, style, and template.
+ *
+ * @param {string} tagName The name of the tag. Only tag names consisting of
+ *     [a-zA-Z0-9-] are allowed. Tag names documented above are disallowed.
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=}
+ *     opt_attributes Mapping from attribute names to their values. Only
+ *     attribute names consisting of [a-zA-Z0-9-] are allowed. Value of null or
+ *     undefined causes the attribute to be omitted.
+ * @param {!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>=} opt_content Content to
+ *     HTML-escape and put inside the tag. This must be empty for void tags
+ *     like <br>. Array elements are concatenated.
+ * @return {!goog.html.SafeHtml} The SafeHtml content with the tag.
+ * @throws {Error} If invalid tag name, attribute name, or attribute value is
+ *     provided.
+ * @throws {goog.asserts.AssertionError} If content for void tag is provided.
+ */
+goog.html.SafeHtml.create = function(tagName, opt_attributes, opt_content) {
+  if (!goog.html.SafeHtml.VALID_NAMES_IN_TAG_.test(tagName)) {
+    throw Error('Invalid tag name <' + tagName + '>.');
+  }
+  if (tagName.toUpperCase() in goog.html.SafeHtml.NOT_ALLOWED_TAG_NAMES_) {
+    throw Error('Tag name <' + tagName + '> is not allowed for SafeHtml.');
+  }
+  return goog.html.SafeHtml.createSafeHtmlTagSecurityPrivateDoNotAccessOrElse(
+      tagName, opt_attributes, opt_content);
+};
+
+
+/**
+ * Creates a SafeHtml representing an iframe tag.
+ *
+ * By default the sandbox attribute is set to an empty value, which is the most
+ * secure option, as it confers the iframe the least privileges. If this
+ * is too restrictive then granting individual privileges is the preferable
+ * option. Unsetting the attribute entirely is the least secure option and
+ * should never be done unless it's stricly necessary.
+ *
+ * @param {goog.html.TrustedResourceUrl=} opt_src The value of the src
+ *     attribute. If null or undefined src will not be set.
+ * @param {goog.html.SafeHtml=} opt_srcdoc The value of the srcdoc attribute.
+ *     If null or undefined srcdoc will not be set.
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=}
+ *     opt_attributes Mapping from attribute names to their values. Only
+ *     attribute names consisting of [a-zA-Z0-9-] are allowed. Value of null or
+ *     undefined causes the attribute to be omitted.
+ * @param {!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>=} opt_content Content to
+ *     HTML-escape and put inside the tag. Array elements are concatenated.
+ * @return {!goog.html.SafeHtml} The SafeHtml content with the tag.
+ * @throws {Error} If invalid tag name, attribute name, or attribute value is
+ *     provided. If opt_attributes contains the src or srcdoc attributes.
+ */
+goog.html.SafeHtml.createIframe = function(
+    opt_src, opt_srcdoc, opt_attributes, opt_content) {
+  var fixedAttributes = {};
+  fixedAttributes['src'] = opt_src || null;
+  fixedAttributes['srcdoc'] = opt_srcdoc || null;
+  var defaultAttributes = {'sandbox': ''};
+  var attributes = goog.html.SafeHtml.combineAttributes(
+      fixedAttributes, defaultAttributes, opt_attributes);
+  return goog.html.SafeHtml.createSafeHtmlTagSecurityPrivateDoNotAccessOrElse(
+      'iframe', attributes, opt_content);
+};
+
+
+/**
+ * Creates a SafeHtml representing a style tag. The type attribute is set
+ * to "text/css".
+ * @param {!goog.html.SafeStyleSheet|!Array<!goog.html.SafeStyleSheet>}
+ *     styleSheet Content to put inside the tag. Array elements are
+ *     concatenated.
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=}
+ *     opt_attributes Mapping from attribute names to their values. Only
+ *     attribute names consisting of [a-zA-Z0-9-] are allowed. Value of null or
+ *     undefined causes the attribute to be omitted.
+ * @return {!goog.html.SafeHtml} The SafeHtml content with the tag.
+ * @throws {Error} If invalid attribute name or attribute value is provided. If
+ *     opt_attributes contains the type attribute.
+ */
+goog.html.SafeHtml.createStyle = function(styleSheet, opt_attributes) {
+  var fixedAttributes = {'type': 'text/css'};
+  var defaultAttributes = {};
+  var attributes = goog.html.SafeHtml.combineAttributes(
+      fixedAttributes, defaultAttributes, opt_attributes);
+
+  var content = '';
+  styleSheet = goog.array.concat(styleSheet);
+  for (var i = 0; i < styleSheet.length; i++) {
+    content += goog.html.SafeStyleSheet.unwrap(styleSheet[i]);
+  }
+  // Convert to SafeHtml so that it's not HTML-escaped.
+  var htmlContent = goog.html.SafeHtml
+      .createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+          content, goog.i18n.bidi.Dir.NEUTRAL);
+  return goog.html.SafeHtml.createSafeHtmlTagSecurityPrivateDoNotAccessOrElse(
+      'style', attributes, htmlContent);
+};
+
+
+/**
+ * @param {string} tagName The tag name.
+ * @param {string} name The attribute name.
+ * @param {!goog.html.SafeHtml.AttributeValue_} value The attribute value.
+ * @return {string} A "name=value" string.
+ * @throws {Error} If attribute value is unsafe for the given tag and attribute.
+ * @private
+ */
+goog.html.SafeHtml.getAttrNameAndValue_ = function(tagName, name, value) {
+  // If it's goog.string.Const, allow any valid attribute name.
+  if (value instanceof goog.string.Const) {
+    value = goog.string.Const.unwrap(value);
+  } else if (name.toLowerCase() == 'style') {
+    value = goog.html.SafeHtml.getStyleValue_(value);
+  } else if (/^on/i.test(name)) {
+    // TODO(jakubvrana): Disallow more attributes with a special meaning.
+    throw Error('Attribute "' + name +
+        '" requires goog.string.Const value, "' + value + '" given.');
+  // URL attributes handled differently accroding to tag.
+  } else if (name.toLowerCase() in goog.html.SafeHtml.URL_ATTRIBUTES_) {
+    if (value instanceof goog.html.TrustedResourceUrl) {
+      value = goog.html.TrustedResourceUrl.unwrap(value);
+    } else if (value instanceof goog.html.SafeUrl) {
+      value = goog.html.SafeUrl.unwrap(value);
+    } else if (goog.isString(value)) {
+      value = goog.html.SafeUrl.sanitize(value).getTypedStringValue();
+    } else {
+      throw Error('Attribute "' + name + '" on tag "' + tagName +
+          '" requires goog.html.SafeUrl, goog.string.Const, or string,' +
+          ' value "' + value + '" given.');
+    }
+  }
+
+  // Accept SafeUrl, TrustedResourceUrl, etc. for attributes which only require
+  // HTML-escaping.
+  if (value.implementsGoogStringTypedString) {
+    // Ok to call getTypedStringValue() since there's no reliance on the type
+    // contract for security here.
+    value = value.getTypedStringValue();
+  }
+
+  goog.asserts.assert(goog.isString(value) || goog.isNumber(value),
+      'String or number value expected, got ' +
+      (typeof value) + ' with value: ' + value);
+  return name + '="' + goog.string.htmlEscape(String(value)) + '"';
+};
+
+
+/**
+ * Gets value allowed in "style" attribute.
+ * @param {goog.html.SafeHtml.AttributeValue_} value It could be SafeStyle or a
+ *     map which will be passed to goog.html.SafeStyle.create.
+ * @return {string} Unwrapped value.
+ * @throws {Error} If string value is given.
+ * @private
+ */
+goog.html.SafeHtml.getStyleValue_ = function(value) {
+  if (!goog.isObject(value)) {
+    throw Error('The "style" attribute requires goog.html.SafeStyle or map ' +
+        'of style properties, ' + (typeof value) + ' given: ' + value);
+  }
+  if (!(value instanceof goog.html.SafeStyle)) {
+    // Process the property bag into a style object.
+    value = goog.html.SafeStyle.create(value);
+  }
+  return goog.html.SafeStyle.unwrap(value);
+};
+
+
+/**
+ * Creates a SafeHtml content with known directionality consisting of a tag with
+ * optional attributes and optional content.
+ * @param {!goog.i18n.bidi.Dir} dir Directionality.
+ * @param {string} tagName
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=} opt_attributes
+ * @param {!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>=} opt_content
+ * @return {!goog.html.SafeHtml} The SafeHtml content with the tag.
+ */
+goog.html.SafeHtml.createWithDir = function(dir, tagName, opt_attributes,
+    opt_content) {
+  var html = goog.html.SafeHtml.create(tagName, opt_attributes, opt_content);
+  html.dir_ = dir;
+  return html;
+};
+
+
+/**
+ * Creates a new SafeHtml object by concatenating values.
+ * @param {...(!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>)} var_args Values to concatenate.
+ * @return {!goog.html.SafeHtml}
+ */
+goog.html.SafeHtml.concat = function(var_args) {
+  var dir = goog.i18n.bidi.Dir.NEUTRAL;
+  var content = '';
+
+  /**
+   * @param {!goog.html.SafeHtml.TextOrHtml_|
+   *     !Array<!goog.html.SafeHtml.TextOrHtml_>} argument
+   */
+  var addArgument = function(argument) {
+    if (goog.isArray(argument)) {
+      goog.array.forEach(argument, addArgument);
+    } else {
+      var html = goog.html.SafeHtml.htmlEscape(argument);
+      content += goog.html.SafeHtml.unwrap(html);
+      var htmlDir = html.getDirection();
+      if (dir == goog.i18n.bidi.Dir.NEUTRAL) {
+        dir = htmlDir;
+      } else if (htmlDir != goog.i18n.bidi.Dir.NEUTRAL && dir != htmlDir) {
+        dir = null;
+      }
+    }
+  };
+
+  goog.array.forEach(arguments, addArgument);
+  return goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+      content, dir);
+};
+
+
+/**
+ * Creates a new SafeHtml object with known directionality by concatenating the
+ * values.
+ * @param {!goog.i18n.bidi.Dir} dir Directionality.
+ * @param {...(!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>)} var_args Elements of array
+ *     arguments would be processed recursively.
+ * @return {!goog.html.SafeHtml}
+ */
+goog.html.SafeHtml.concatWithDir = function(dir, var_args) {
+  var html = goog.html.SafeHtml.concat(goog.array.slice(arguments, 1));
+  html.dir_ = dir;
+  return html;
+};
+
+
+/**
+ * Type marker for the SafeHtml type, used to implement additional run-time
+ * type checking.
+ * @const
+ * @private
+ */
+goog.html.SafeHtml.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ = {};
+
+
+/**
+ * Package-internal utility method to create SafeHtml instances.
+ *
+ * @param {string} html The string to initialize the SafeHtml object with.
+ * @param {?goog.i18n.bidi.Dir} dir The directionality of the SafeHtml to be
+ *     constructed, or null if unknown.
+ * @return {!goog.html.SafeHtml} The initialized SafeHtml object.
+ * @package
+ */
+goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse = function(
+    html, dir) {
+  return new goog.html.SafeHtml().initSecurityPrivateDoNotAccessOrElse_(
+      html, dir);
+};
+
+
+/**
+ * Called from createSafeHtmlSecurityPrivateDoNotAccessOrElse(). This
+ * method exists only so that the compiler can dead code eliminate static
+ * fields (like EMPTY) when they're not accessed.
+ * @param {string} html
+ * @param {?goog.i18n.bidi.Dir} dir
+ * @return {!goog.html.SafeHtml}
+ * @private
+ */
+goog.html.SafeHtml.prototype.initSecurityPrivateDoNotAccessOrElse_ = function(
+    html, dir) {
+  this.privateDoNotAccessOrElseSafeHtmlWrappedValue_ = html;
+  this.dir_ = dir;
+  return this;
+};
+
+
+/**
+ * Like create() but does not restrict which tags can be constructed.
+ *
+ * @param {string} tagName Tag name. Set or validated by caller.
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=} opt_attributes
+ * @param {(!goog.html.SafeHtml.TextOrHtml_|
+ *     !Array<!goog.html.SafeHtml.TextOrHtml_>)=} opt_content
+ * @return {!goog.html.SafeHtml}
+ * @throws {Error} If invalid or unsafe attribute name or value is provided.
+ * @throws {goog.asserts.AssertionError} If content for void tag is provided.
+ * @package
+ */
+goog.html.SafeHtml.createSafeHtmlTagSecurityPrivateDoNotAccessOrElse =
+    function(tagName, opt_attributes, opt_content) {
+  var dir = null;
+  var result = '<' + tagName;
+
+  if (opt_attributes) {
+    for (var name in opt_attributes) {
+      if (!goog.html.SafeHtml.VALID_NAMES_IN_TAG_.test(name)) {
+        throw Error('Invalid attribute name "' + name + '".');
+      }
+      var value = opt_attributes[name];
+      if (!goog.isDefAndNotNull(value)) {
+        continue;
+      }
+      result += ' ' +
+          goog.html.SafeHtml.getAttrNameAndValue_(tagName, name, value);
+    }
+  }
+
+  var content = opt_content;
+  if (!goog.isDefAndNotNull(content)) {
+    content = [];
+  } else if (!goog.isArray(content)) {
+    content = [content];
+  }
+
+  if (goog.dom.tags.isVoidTag(tagName.toLowerCase())) {
+    goog.asserts.assert(!content.length,
+        'Void tag <' + tagName + '> does not allow content.');
+    result += '>';
+  } else {
+    var html = goog.html.SafeHtml.concat(content);
+    result += '>' + goog.html.SafeHtml.unwrap(html) + '</' + tagName + '>';
+    dir = html.getDirection();
+  }
+
+  var dirAttribute = opt_attributes && opt_attributes['dir'];
+  if (dirAttribute) {
+    if (/^(ltr|rtl|auto)$/i.test(dirAttribute)) {
+      // If the tag has the "dir" attribute specified then its direction is
+      // neutral because it can be safely used in any context.
+      dir = goog.i18n.bidi.Dir.NEUTRAL;
+    } else {
+      dir = null;
+    }
+  }
+
+  return goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+      result, dir);
+};
+
+
+/**
+ * @param {!Object<string, string>} fixedAttributes
+ * @param {!Object<string, string>} defaultAttributes
+ * @param {!Object<string, goog.html.SafeHtml.AttributeValue_>=}
+ *     opt_attributes Optional attributes passed to create*().
+ * @return {!Object<string, goog.html.SafeHtml.AttributeValue_>}
+ * @throws {Error} If opt_attributes contains an attribute with the same name
+ *     as an attribute in fixedAttributes.
+ * @package
+ */
+goog.html.SafeHtml.combineAttributes = function(
+    fixedAttributes, defaultAttributes, opt_attributes) {
+  var combinedAttributes = {};
+  var name;
+
+  for (name in fixedAttributes) {
+    goog.asserts.assert(name.toLowerCase() == name, 'Must be lower case');
+    combinedAttributes[name] = fixedAttributes[name];
+  }
+  for (name in defaultAttributes) {
+    goog.asserts.assert(name.toLowerCase() == name, 'Must be lower case');
+    combinedAttributes[name] = defaultAttributes[name];
+  }
+
+  for (name in opt_attributes) {
+    var nameLower = name.toLowerCase();
+    if (nameLower in fixedAttributes) {
+      throw Error('Cannot override "' + nameLower + '" attribute, got "' +
+          name + '" with value "' + opt_attributes[name] + '"');
+    }
+    if (nameLower in defaultAttributes) {
+      delete combinedAttributes[nameLower];
+    }
+    combinedAttributes[name] = opt_attributes[name];
+  }
+
+  return combinedAttributes;
+};
+
+
+/**
+ * A SafeHtml instance corresponding to the HTML doctype: "<!DOCTYPE html>".
+ * @const {!goog.html.SafeHtml}
+ */
+goog.html.SafeHtml.DOCTYPE_HTML =
+    goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+        '<!DOCTYPE html>', goog.i18n.bidi.Dir.NEUTRAL);
+
+
+/**
+ * A SafeHtml instance corresponding to the empty string.
+ * @const {!goog.html.SafeHtml}
+ */
+goog.html.SafeHtml.EMPTY =
+    goog.html.SafeHtml.createSafeHtmlSecurityPrivateDoNotAccessOrElse(
+        '', goog.i18n.bidi.Dir.NEUTRAL);