Add //ui/snapshot to browser deps if aura is enabled.

When building chromium with use_aura=true, it is possible
that //ui/snapshot is not added as a dependency, resulting in build
errors like:
/usr/bin/ld.bfd: obj/chrome/browser/libbrowser.a
(native_desktop_media_list.o): undefined reference to symbol
'_ZN2ui31GrabWindowSnapshotAndScaleAsyncEPN4aura6WindowERKN3gfx...
This is because there is USE_AURA conditional code in
native_desktop_media_list.cc.

BUG=

Review-Url: https://codereview.chromium.org/2476003002
Cr-Commit-Position: refs/heads/master@{#431899}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 32ad6dab..b7f47f0 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -2215,6 +2215,7 @@
       "//services/ui/public/cpp/input_devices",
       "//ui/aura",
       "//ui/compositor",
+      "//ui/snapshot",
       "//ui/views/mus",
     ]
   }