Bug 591246 - Move towards shell-black02 mockup

Remove the last use of passing width into Dash by having the
Pane with the previews scaling dynamically and relying on
Clutter scaling.

If we only have one workspace, don't display a selection frame
for it.

Rework Dash into a searchArea and sectionArea, which get
explicitly sized by overlay.js.  We use the workspaces size
to choose the size of those dash areas.

Switch dash colors/boxes etc. to ones from shell-black02.

Add a gradient to the panel.

Add a magnifier.svg for use in search.

js/ui/workspaces.js

@@ -398,7 +398,9 @@ Workspace.prototype = {
 
     // Mark the workspace selected/not-selected
     setSelected : function(selected) {
-        if (selected) {
+        let global = Shell.Global.get();
+        // Don't draw a frame if we only have one workspace
+        if (selected && global.screen.n_workspaces > 1) {
             if (this._frame)
                 return;
 
@@ -1112,6 +1114,11 @@ Workspaces.prototype = {
 
             // FIXME: deal with windows on the lost workspaces
         }
+
+        // Reset the selection state; if we went from > 1 workspace to 1,
+        // this has the side effect of removing the frame border
+        let activeIndex = global.screen.get_active_workspace_index();
+        this._workspaces[activeIndex].setSelected(true);
     },
 
     _activeWorkspaceChanged : function(wm, from, to, direction) {