ash/mash: Introduce a ShelfDelegate implementation for mash.

ash/screen_util.cc

Index: ash/screen_util.cc
diff --git a/ash/screen_util.cc b/ash/screen_util.cc
index c27d896e52cb2e107fb31b7c1515aba754dc14f5..d82298c7eac5c4baaf39fe7b5d6cf0fc98b11de2 100644
--- a/ash/screen_util.cc
+++ b/ash/screen_util.cc
@@ -65,6 +65,14 @@ gfx::Rect ScreenUtil::GetShelfDisplayBoundsInRoot(aura::Window* window) {
     size.Scale(scale, scale);
     return gfx::Rect(gfx::ToCeiledSize(size));
   } else {
+    if (window->GetRootWindow()->bounds().IsEmpty()) {
+      // TODO(sad): This only happens when running with mustash, since the
+      // root-window here refers to the shelf Widget, which has not been
+      // sized/positioned yet. Use the bounds of the display in this case.

[msw, 2016/02/09 18:31:26]

Could this always use the display bounds? When are they different?

[sadrul, 2016/02/10 08:04:41]

Looks like it could always use the display bounds (at least, the trybots aren't
complaining: https://codereview.chromium.org/1688453002/). However, it doesn't
work right for mustash if we always use the display size. I haven't looked
closely enough to figure out why. But ideally, as sky@ notes below, we wouldn't
be running this code for mustash at all.

+      gfx::Display display =

[sky, 2016/02/09 20:44:08]

We shouldn't be calling this code right? I think it best to add a NOTIMPLEMENTED
or warning that we need to fix this.

[sadrul, 2016/02/10 08:04:41]

Added a NOTIMPLEMENTED() here. We do still need this temporary workaround to get
the shelf to show up on screen at the right position though, so I kept that
part.

+          gfx::Screen::GetScreen()->GetDisplayNearestWindow(window);
+      return gfx::Rect(display.size());
+    }
     return window->GetRootWindow()->bounds();
   }
 }