Consistently use string for string data types in JSDoc comments

Sometimes we also used `String`, but `string` is the what the JSDoc
documentation recommends.

extensions/chromium/pdfHandler-vcros.js

@@ -28,7 +28,7 @@ limitations under the License.
   /**
    * Invoked when "Open with PDF Viewer" is chosen in the File browser.
    *
-   * @param {String} id      File browser action ID as specified in
+   * @param {string} id      File browser action ID as specified in
    *                         manifest.json
    * @param {Object} details Object of type FileHandlerExecuteEventDetails
    */

src/shared/message_handler.js

@@ -132,7 +132,7 @@ MessageHandler.prototype = {
   },
   /**
    * Sends a message to the comObj to invoke the action with the supplied data.
-   * @param {String} actionName - Action to call.
+   * @param {string} actionName - Action to call.
    * @param {JSON} data - JSON data to send.
    * @param {Array} [transfers] - Optional list of transfers/ArrayBuffers
    */
@@ -147,7 +147,7 @@ MessageHandler.prototype = {
   /**
    * Sends a message to the comObj to invoke the action with the supplied data.
    * Expects that the other side will callback with the response.
-   * @param {String} actionName - Action to call.
+   * @param {string} actionName - Action to call.
    * @param {JSON} data - JSON data to send.
    * @param {Array} [transfers] - Optional list of transfers/ArrayBuffers.
    * @returns {Promise} Promise to be resolved with response data.
@@ -172,7 +172,7 @@ MessageHandler.prototype = {
   /**
    * Sends a message to the comObj to invoke the action with the supplied data.
    * Expect that the other side will callback to signal 'start_complete'.
-   * @param {String} actionName - Action to call.
+   * @param {string} actionName - Action to call.
    * @param {JSON} data - JSON data to send.
    * @param {Object} queueingStrategy - strategy to signal backpressure based on
    *                 internal queue.

web/app.js

@@ -764,7 +764,7 @@ let PDFViewerApplication = {
 
   /**
    * Show the error box.
-   * @param {String} message A message that is human readable.
+   * @param {string} message A message that is human readable.
    * @param {Object} moreInfo (optional) Further information about the error
    *                            that is more technical.  Should have a 'message'
    *                            and optionally a 'stack' property.

web/chromecom.js

@@ -30,8 +30,8 @@ let ChromeCom = {
    * Creates an event that the extension is listening for and will
    * asynchronously respond by calling the callback.
    *
-   * @param {String} action The action to trigger.
-   * @param {String} data Optional data to send.
+   * @param {string} action The action to trigger.
+   * @param {string} data Optional data to send.
    * @param {Function} callback Optional response callback that will be called
    * with one data argument. When the request cannot be handled, the callback
    * is immediately invoked with no arguments.
@@ -56,7 +56,7 @@ let ChromeCom = {
   /**
    * Resolves a PDF file path and attempts to detects length.
    *
-   * @param {String} file - Absolute URL of PDF file.
+   * @param {string} file - Absolute URL of PDF file.
    * @param {OverlayManager} overlayManager - Manager for the viewer overlays.
    * @param {Function} callback - A callback with resolved URL and file length.
    */

web/firefoxcom.js

@@ -32,8 +32,8 @@ let FirefoxCom = (function FirefoxComClosure() {
      * synchronously respond to.
      * NOTE: It is reccomended to use request() instead since one day we may not
      * be able to synchronously reply.
-     * @param {String} action The action to trigger.
-     * @param {String} data Optional data to send.
+     * @param {string} action The action to trigger.
+     * @param {string} data Optional data to send.
      * @return {*} The response.
      */
     requestSync(action, data) {
@@ -52,8 +52,8 @@ let FirefoxCom = (function FirefoxComClosure() {
     /**
      * Creates an event that the extension is listening for and will
      * asynchronously respond by calling the callback.
-     * @param {String} action The action to trigger.
-     * @param {String} data Optional data to send.
+     * @param {string} action The action to trigger.
+     * @param {string} data Optional data to send.
      * @param {Function} callback Optional response callback that will be called
      * with one data argument.
      */

web/pdf_link_service.js

@@ -189,7 +189,7 @@ class PDFLinkService {
   /**
    * Prefix the full url on anchor links to make sure that links are resolved
    * relative to the current URL instead of the one defined in <base href>.
-   * @param {String} anchor The anchor hash, including the #.
+   * @param {string} anchor The anchor hash, including the #.
    * @returns {string} The hyperlink to the PDF object.
    */
   getAnchorUrl(anchor) {