Make ui gn check pass. Misc GN build improvements.

Content/public/app was messed up and didn't link everything properly, so this separates it out into browser and child like content/app is.

R=jamesr@chromium.org
Reland of https://codereview.chromium.org/545313002/ but with public/utility dependency added

TBR=jamesr@chromium.org

Review URL: https://codereview.chromium.org/549863004

Cr-Commit-Position: refs/heads/master@{#293646}

diff --git a/ui/aura/BUILD.gn b/ui/aura/BUILD.gn
index b5f08499f..10962d3 100644
--- a/ui/aura/BUILD.gn
+++ b/ui/aura/BUILD.gn

@@ -183,6 +183,7 @@
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx/geometry",
+    "//ui/wm",
   ]
 
   if (is_win) {