Login: Stop motion stills when not selected.

This updates the user image URL handler to respect
frame arguments for motion stills and not only the
default set of user images.

Bug: 775988
Test: manual
Change-Id: I25b9e5d0d3937c90b128b246ba40c63bb59a4b51
Reviewed-on: https://chromium-review.googlesource.com/726600Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509923}

chrome/browser/ui/webui/chromeos/user_image_source.cc

@@ -72,7 +72,7 @@ scoped_refptr<base::RefCountedMemory> LoadUserImageFrameForScaleFactor(
     return ui::ResourceBundle::GetSharedInstance()
         .LoadDataResourceBytesForScale(resource_id, scale_factor);
   }
-  // TODO(reveman): Add support frames beyond 0 (crbug.com/750064).
+  // TODO(reveman): Add support for frames beyond 0 (crbug.com/750064).
   if (frame) {
     NOTIMPLEMENTED() << "Unsupported frame: " << frame;
     return nullptr;
@@ -87,6 +87,33 @@ scoped_refptr<base::RefCountedMemory> LoadUserImageFrameForScaleFactor(
   return data;
 }
 
+scoped_refptr<base::RefCountedMemory> GetUserImageFrame(
+    scoped_refptr<base::RefCountedMemory> image_bytes,
+    user_manager::UserImage::ImageFormat image_format,
+    int frame) {
+  // Return all frames.
+  if (frame == -1)
+    return image_bytes;
+  // TODO(reveman): Add support for frames beyond 0 (crbug.com/750064).
+  if (frame) {
+    NOTIMPLEMENTED() << "Unsupported frame: " << frame;
+    return nullptr;
+  }
+  // Only PNGs can be animated.
+  if (image_format != user_manager::UserImage::FORMAT_PNG)
+    return image_bytes;
+  // Extract first frame by re-encoding image.
+  SkBitmap bitmap;
+  if (!gfx::PNGCodec::Decode(image_bytes->front(), image_bytes->size(),
+                             &bitmap)) {
+    return nullptr;
+  }
+  scoped_refptr<base::RefCountedBytes> data(new base::RefCountedBytes);
+  gfx::PNGCodec::EncodeBGRASkBitmap(bitmap, false /* discard transparency */,
+                                    &data->data());
+  return data;
+}
+
 scoped_refptr<base::RefCountedMemory> GetUserImageInternal(
     const AccountId& account_id,
     int frame) {
@@ -103,8 +130,10 @@ scoped_refptr<base::RefCountedMemory> GetUserImageInternal(
   }
 
   if (user) {
-    if (user->has_image_bytes())
-      return user->image_bytes();
+    if (user->has_image_bytes()) {
+      return GetUserImageFrame(user->image_bytes(), user->image_format(),
+                               frame);
+    }
     if (user->image_is_stub()) {
       return LoadUserImageFrameForScaleFactor(IDR_LOGIN_DEFAULT_USER, frame,
                                               scale_factor);