diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index 8cdb06b6..80fe7e38 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1010,7 +1010,7 @@ Blockly.WorkspaceSvg.prototype.showContextMenu_ = function(e) {
         deleteNext();
       } else {
         Blockly.confirm(Blockly.Msg.DELETE_ALL_BLOCKS.
-            replace('%1',String(deleteList.length)),
+            replace('%1', deleteList.length),
             function(ok) {
               if (ok) {
                 deleteNext();
diff --git a/demos/custom-dialogs/custom-dialog.js b/demos/custom-dialogs/custom-dialog.js
index 77a79660..1892303a 100644
--- a/demos/custom-dialogs/custom-dialog.js
+++ b/demos/custom-dialogs/custom-dialog.js
@@ -17,55 +17,62 @@
  * limitations under the License.
  */
 
-CustomDialog = {}
+/**
+ * An example implementation of how one might replace Blockly's browser
+ * dialogs. This is just an example, and applications are not encouraged to use
+ * it verbatim.
+ *
+ * @namespace
+ */
+CustomDialog = {};
 
 /** Override Blockly.alert() with custom implementation. */
 Blockly.alert = function(message, callback) {
-    console.log('Alert: ' + message);
-    CustomDialog.show('Alert', message, {
-        onCancel: callback
-    });
+  console.log('Alert: ' + message);
+  CustomDialog.show('Alert', message, {
+    onCancel: callback
+  });
 };
 
 /** Override Blockly.confirm() with custom implementation. */
 Blockly.confirm = function(message, callback) {
-    console.log('Confirm: ' + message);
-    CustomDialog.show('Confirm', message, {
-        showOkay: true,
-        onOkay: function() {
-            callback(true)
-        },
-        showCancel: true,
-        onCancel: function() {
-            callback(false)
-        }
-    });
+  console.log('Confirm: ' + message);
+  CustomDialog.show('Confirm', message, {
+    showOkay: true,
+    onOkay: function() {
+      callback(true)
+    },
+    showCancel: true,
+    onCancel: function() {
+      callback(false)
+    }
+  });
 };
 
 /** Override Blockly.prompt() with custom implementation. */
 Blockly.prompt = function(message, defaultValue, callback) {
-    console.log('Prompt: ' + message);
-    CustomDialog.show('Prompt', message, {
-        showInput: true,
-        showOkay: true,
-        onOkay: function() {
-            callback(CustomDialog.inputField.value)
-        },
-        showCancel: true,
-        onCancel: function() {
-            callback(null)
-        }
-    });
-    CustomDialog.inputField.value = defaultValue;
+  console.log('Prompt: ' + message);
+  CustomDialog.show('Prompt', message, {
+    showInput: true,
+    showOkay: true,
+    onOkay: function() {
+      callback(CustomDialog.inputField.value)
+    },
+    showCancel: true,
+    onCancel: function() {
+      callback(null)
+    }
+  });
+  CustomDialog.inputField.value = defaultValue;
 };
 
-
+/** Hides any currently visible dialog. */
 CustomDialog.hide = function() {
-    if (CustomDialog.backdropDiv_) {
-        CustomDialog.backdropDiv_.style.display = 'none'
-        CustomDialog.dialogDiv_.style.display = 'none'
-    }
-}
+  if (CustomDialog.backdropDiv_) {
+    CustomDialog.backdropDiv_.style.display = 'none'
+    CustomDialog.dialogDiv_.style.display = 'none'
+  }
+};
 
 /**
  * Shows the dialog.
@@ -74,90 +81,93 @@ CustomDialog.hide = function() {
  *  - showCancel: Whether to show the Cancel button.
  *  - showInput: Whether to show the text input field.
  *  - onOkay: Callback to handle the okay button.
- *  - onCancel: Callback to handle the cancel button.
+ *  - onCancel: Callback to handle the cancel button and backdrop clicks.
  */
 CustomDialog.show = function(title, message, options) {
-    var backdropDiv = CustomDialog.backdropDiv_;
-    var dialogDiv = CustomDialog.dialogDiv_;
-    if (!dialogDiv) {
-        // Generate HTML
-        var body = document.getElementsByTagName('body')[0];
-        backdropDiv = document.createElement('div');
-        backdropDiv.setAttribute('id', 'backdrop');
-        backdropDiv.style.cssText =
-              'position: absolute;'
-              + 'top: 0px;'
-              + 'left: 0px;'
-              + 'right: 0px;'
-              + 'bottom: 0px;'
-              + 'background-color: rgba(0, 0, 0, 0.7);';
-        body.appendChild(backdropDiv);
+  var backdropDiv = CustomDialog.backdropDiv_;
+  var dialogDiv = CustomDialog.dialogDiv_;
+  if (!dialogDiv) {
+    // Generate HTML
+    backdropDiv = document.createElement('div');
+    backdropDiv.id = 'customDialogBackdrop';
+    backdropDiv.style.cssText =
+        'position: absolute;' +
+        'top: 0; left: 0; right: 0; bottom: 0;' +
+        'background-color: rgba(0, 0, 0, .7);';
+    document.body.appendChild(backdropDiv);
 
-        dialogDiv = document.createElement('div');
-        dialogDiv.setAttribute('id', 'dialog');
-        dialogDiv.style.cssText =
-                'background-color: white;'
-                + 'width: 400px;'
-                + 'margin: 20px auto 0;'
-                + 'padding: 10px;';
-        backdropDiv.appendChild(dialogDiv);
+    dialogDiv = document.createElement('div');
+    dialogDiv.id = 'customDialog';
+    dialogDiv.style.cssText =
+        'background-color: #fff;' +
+        'width: 400px;' +
+        'margin: 20px auto 0;' +
+        'padding: 10px;';
+    backdropDiv.appendChild(dialogDiv);
 
-        dialogDiv.onclick = function(event) {
-            event.stopPropagation();
-        };
-
-        CustomDialog.backdropDiv_ = backdropDiv;
-        CustomDialog.dialogDiv_ = dialogDiv;
-    }
-    backdropDiv.style.display = 'block';
-    dialogDiv.style.display = 'block';
-
-    dialogDiv.innerHTML = '<div id="dialogTitle"><strong>' + title + '</strong></div>'
-            + '<p>' + message + '</p>'
-            + (options.showInput? '<div><input id="dialogInput"></div>' : '')
-            + '<div class="buttons">'
-            + (options.showCancel ? '<button id="dialogCancel">Cancel</button>': '')
-            + (options.showOkay ? '<button id="dialogOkay">OK</button>': '')
-            + '</div>';
-
-    var onOkay = function(event) {
-        CustomDialog.hide();
-        options.onOkay && options.onOkay();
-        event && event.stopPropagation();
-    };
-    var onCancel = function(event) {
-        CustomDialog.hide();
-        options.onCancel && options.onCancel();
-        event && event.stopPropagation();
+    dialogDiv.onclick = function(event) {
+      event.stopPropagation();
     };
 
-    var dialogInput = document.getElementById('dialogInput');
-    CustomDialog.inputField = dialogInput;
-    if (dialogInput) {
-        dialogInput.focus();
+    CustomDialog.backdropDiv_ = backdropDiv;
+    CustomDialog.dialogDiv_ = dialogDiv;
+  }
+  backdropDiv.style.display = 'block';
+  dialogDiv.style.display = 'block';
 
-        dialogInput.onkeyup = function(event) {
-            if (event.keyCode == 13) {
-                // Process as OK when user hits enter.
-                onOkay();
-                return false;
-            } else if (event.keyCode == 27)  {
-                // Process as cancel when user hits esc.
-                onCancel();
-                return false;
-            }
-        };
-    } else {
-        var okay = document.getElementById('dialogOkay');
-        okay && okay.focus();
-    }
+  dialogDiv.innerHTML =
+      '<header class="customDialogTitle"></header>' +
+      '<p class="customDialogMessage"></p>' +
+      (options.showInput ? '<div><input id="customDialogInput"></div>' : '') +
+      '<div class="customDialogButtons">' +
+      (options.showCancel ? '<button id="customDialogCancel">Cancel</button>': '') +
+      (options.showOkay ? '<button id="customDialogOkay">OK</button>': '') +
+      '</div>';
+  dialogDiv.getElementsByClassName('customDialogTitle')[0]
+      .appendChild(document.createTextNode(title));
+  dialogDiv.getElementsByClassName('customDialogMessage')[0]
+      .appendChild(document.createTextNode(message));
 
-    if (options.showOkay) {
-        document.getElementById('dialogOkay').onclick = onOkay;
-    }
-    if (options.showCancel) {
-        document.getElementById('dialogCancel').onclick = onCancel;
-    }
+  var onOkay = function(event) {
+    CustomDialog.hide();
+    options.onOkay && options.onOkay();
+    event && event.stopPropagation();
+  };
+  var onCancel = function(event) {
+    CustomDialog.hide();
+    options.onCancel && options.onCancel();
+    event && event.stopPropagation();
+  };
 
-    backdropDiv.onclick = onCancel;
-}
+  var dialogInput = document.getElementById('customDialogInput');
+  CustomDialog.inputField = dialogInput;
+  if (dialogInput) {
+    dialogInput.focus();
+
+    dialogInput.onkeyup = function(event) {
+      if (event.keyCode == 13) {
+        // Process as OK when user hits enter.
+        onOkay();
+        return false;
+      } else if (event.keyCode == 27)  {
+        // Process as cancel when user hits esc.
+        onCancel();
+        return false;
+      }
+    };
+  } else {
+    var okay = document.getElementById('customDialogOkay');
+    okay && okay.focus();
+  }
+
+  if (options.showOkay) {
+    document.getElementById('customDialogOkay')
+        .addEventListener('click', onOkay);
+  }
+  if (options.showCancel) {
+    document.getElementById('customDialogCancel')
+        .addEventListener('click', onCancel);
+  }
+
+  backdropDiv.onclick = onCancel;
+};