The webapp uses localStorage to decide whether logging to the server

remoting/webapp/me2mom/log_to_server.js

Index: remoting/webapp/me2mom/log_to_server.js
diff --git a/remoting/webapp/me2mom/log_to_server.js b/remoting/webapp/me2mom/log_to_server.js
index d42bb7085d06583502aa2a2a8a4aae98ec833be2..017bc1afe21c0ce4816f1a8d4fcb05803e871f53 100644
--- a/remoting/webapp/me2mom/log_to_server.js
+++ b/remoting/webapp/me2mom/log_to_server.js
@@ -17,9 +17,30 @@ var remoting = remoting || {};
  */
 remoting.LogToServer = function() {
   /** @type Array.<string> */ this.pendingEntries = [];
-  /** @type boolean */ this.enabled = false;
 };
 
+// Local storage keys.
+/** @private */
+remoting.LogToServer.prototype.KEY_ENABLED_ = 'remoting.LogToServer.enabled';
+/** @private */
+remoting.LogToServer.prototype.KEY_ID_ = 'remoting.LogToServer.id';
+
+// Constants used for generating an ID.
+/** @private */
+remoting.LogToServer.prototype.ID_ALPHABET_ =
+    'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
+/** @private */
+remoting.LogToServer.prototype.ID_LEN_ = 20;
+
+/**
+ * Enables or disables logging.
+ *
+ * @param {boolean} enabled whether logging is enabled
+ */
+remoting.LogToServer.prototype.setEnabled = function(enabled) {
+  window.localStorage.setItem(this.KEY_ENABLED_, enabled ? 'true' : 'false');
+}
+
 /**
  * Logs a client session state change.
  *
@@ -33,6 +54,7 @@ remoting.LogToServer.prototype.logClientSessionStateChange =
   entry.addHostFields();
   entry.addChromeVersionField();
   entry.addWebappVersionField();
+  entry.addIdField(this.getId());
   this.log(entry);
 };
 
@@ -43,7 +65,7 @@ remoting.LogToServer.prototype.logClientSessionStateChange =
  * @param {remoting.ServerLogEntry} entry
  */
 remoting.LogToServer.prototype.log = function(entry) {
-  if (!this.enabled) {
+  if (!this.isEnabled()) {
     return;
   }
   // Store a stanza for the entry
@@ -62,3 +84,51 @@ remoting.LogToServer.prototype.log = function(entry) {
   remoting.debug.logIq(true, stanza);
   remoting.wcs.sendIq(stanza);
 };
+
+/**
+ * Whether logging is enabled.
+ *
+ * @private
+ * @return {boolean} whether logging is enabled
+ */
+remoting.LogToServer.prototype.isEnabled = function() {
+  var value = window.localStorage.getItem(this.KEY_ENABLED_);
+  return (value == 'true');
+};
+
+/**
+ * Gets an ID from local storage.
+ *
+ * This function returns the empty string if logging is disabled.
+ * If logging is enabled, and there is no ID in local storage, then this
+ * function will create and store an ID.
+ *
+ * @private
+ * @return {string} an ID, or the empty string
+ */
+remoting.LogToServer.prototype.getId = function() {
+  if (!this.isEnabled()) {
+    return '';
+  }
+  var id = window.localStorage.getItem(this.KEY_ID_);
+  if ((!id) || (typeof id != 'string')) {
+    id = this.generateId();
+    window.localStorage.setItem(this.KEY_ID_, id);
+  }
+  return id.toString();
+};
+
+/**
+ * Generates an ID.
+ *
+ * @private
+ * @return {string} an ID
+ */
+remoting.LogToServer.prototype.generateId = function() {
+  var idArray = [];
+  for (var i = 0; i < this.ID_LEN_; i++) {
+    var index = Math.random() * this.ID_ALPHABET_.length;
+    idArray.push(this.ID_ALPHABET_.slice(index, index + 1));

[Jamie, 2011/12/02 20:44:20]

Why not just:

  idArray.push(this.ID_ALPHABET_[index]);

Or even (shorter, but less clear IMO):

  idArray[i] = this.ID_ALPHABET_[index];

[simonmorris, 2011/12/02 21:05:58]

I did it this way only because join() joins strings, not
characters, and I think slice() will use a reference to
the alphabet string. So this way avoids creating lots of
small strings.

+  }
+  return idArray.join('');
+};