Enables WorkspaceLayoutManagerSoloTest.PinnedSuspendsAlwaysOnTop for mash

Now that pinning has been wired up for mash this test can actually be
run in mash.

BUG=622486
TEST=test only change
R=msw@chromium.org

Review-Url: https://codereview.chromium.org/2778373004
Cr-Commit-Position: refs/heads/master@{#460467}

ash/common/wm/workspace/workspace_layout_manager_unittest.cc

@@ -758,10 +758,6 @@ TEST_F(WorkspaceLayoutManagerSoloTest, FullscreenSuspendsAlwaysOnTop) {
 
 // Similary, pinned window causes always_on_top_ windows to stack below.
 TEST_F(WorkspaceLayoutManagerSoloTest, PinnedSuspendsAlwaysOnTop) {
-  // TODO: mash doesn't support pinning yet http://crbug.com/622486.
-  if (WmShell::Get()->IsRunningInMash())
-    return;
-
   gfx::Rect bounds(100, 100, 200, 200);
   std::unique_ptr<aura::Window> pinned_window_owner(
       CreateTestWindowInShellWithBounds(bounds));