Notifications API support for images with multiple scale factors.

chrome/common/extensions/api/notifications.idl

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Use the <code>chrome.notifications</code> API to create rich notifications
 // using templates and show these notifications to users in the system tray.
 namespace notifications {
   [noinline_doc] enum TemplateType {
     // icon, title, message, expandedMessage, up to two buttons
     basic,
@@ skipping 18 matching lines @@
   };
 
   dictionary NotificationItem {
     // Title of one item of a list notification.
     DOMString title;
 
     // Additional details about this item.
     DOMString message;
   };
 
-  [nodoc] dictionary NotificationBitmap {
-    long width;
-    long height;
-    ArrayBuffer? data;
+  // Contains an array of RGBA bitmap data, 32 bits per channel.  |data|
+  // should therefore have a length equal to 4 * width * height.
+  dictionary BitmapData {
+    ArrayBuffer data;
+    double width;
+    double height;
+  };
+
+  dictionary ImageRepresentation {
+    // The pixel ratio for which this bitmap is intended.
+    double scale;
+    // A URL from which the image will be downloaded.
+    (DOMString or BitmapData) data;
   };
 
   dictionary NotificationButton {
     DOMString title;
+    // The icon used with the button.  Either an icon URL or a spec must be
+    // provided.
     DOMString? iconUrl;
-    [nodoc] NotificationBitmap? iconBitmap;
+    ImageRepresentation[]? icons;

[benwells, 2014/06/27 03:15:27]

I think having these names be plural is confusing. There is only one icon being
provided but it is being produced with multiple representations.

Can we call it something like iconReps? Same goes for the notification options.

[dewittj, 2014/07/01 15:06:11]

Done.

   };
 
   dictionary NotificationOptions {
     // Which type of notification to display.
     // <em>Required for $(ref:notifications.create)</em> method.
     TemplateType? type;
 
     // Sender's avatar, app icon, or a thumbnail for image notifications.

[benwells, 2014/06/27 03:15:27]

Are we intending notifications to have app icons here? I thought this would be
more notification specific, with the new app mask being how to communicate the
responsible app.

[dewittj, 2014/07/01 15:06:11]

We haven't been too prescriptive about what is acceptable in each area of the
UI, and I think that's a good thing.  When I've written apps for the
notification center, I frequently use people's images when available, but
generic icons if there isn't a more specific picture for this particular data. 
So probably we should leave this more generic but also publish a
google-style-guide similar to the Android one that has guidelines for app
developers.

See also http://developer.android.com/design/patterns/notifications.html

[benwells, 2014/07/02 03:11:11]

I was thinking about the comment here not the name. I agree we don't want to be
prescriptive, however it might make sense to give guidance in the documentation
about what we think best practices are.

E.g. we could say here that "ideally this is an image for this specific
notification, e.g. avatar or a thumbnail. If there is nothing suitable a generic
app image is acceptable." blah blah blah.

-    // <em>Required for $(ref:notifications.create)</em> method.
+    // Either an iconUrl or a ImageRepresentation must be provided.
     DOMString? iconUrl;
-    [nodoc] NotificationBitmap? iconBitmap;
+    ImageRepresentation[]? icons;
 
     // Title of the notification (e.g. sender name for email).
     // <em>Required for $(ref:notifications.create)</em> method.
     DOMString? title;
 
     // Main notification content.
     // <em>Required for $(ref:notifications.create)</em> method.
     DOMString? message;
 
     // Alternate notification content with a lower-weight font.
     DOMString? contextMessage;
 
     // Priority ranges from -2 to 2. -2 is lowest priority. 2 is highest. Zero
     // is default.
     long? priority;
 
     // A timestamp associated with the notification, in milliseconds past the
     // epoch (e.g. <code>Date.now() + n</code>).
     double? eventTime;
 
     // Text and icons for up to two notification action buttons.
     NotificationButton[]? buttons;
 
-    // Secondary notification content.
-    [nodoc] DOMString? expandedMessage;
+    // Secondary notification content.  This field is deprecated and unused.
+    [deprecated] DOMString? expandedMessage;
 
-    // Image thumbnail for image-type notifications.
+    // Image thumbnail for image-type notifications.  Either an imageUrl or an imageSpec
+    // must be provided.
     DOMString? imageUrl;
-    [nodoc] NotificationBitmap? imageBitmap;
+    ImageRepresentation[]? images;
 
     // Items for multi-item notifications.
     NotificationItem[]? items;
 
     // Current progress ranges from 0 to 100.
     long? progress;
 
     // Whether to show UI indicating that the app will visibly respond to
     // clicks on the body of a notification.
     boolean? isClickable;
@@ skipping 58 matching lines @@
     static void onButtonClicked(DOMString notificationId, long buttonIndex);
 
     // The user changes the permission level.
     static void onPermissionLevelChanged(PermissionLevel level);
 
     // The user clicked on a link for the app's notification settings.
     static void onShowSettings();
   };
 
 };