Use mojo SystemTray interfaces for both mash and classic ash

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index 4b2bef37ba70fba34c7dbc09854e4658222efeb2..b565a4b2ca4672d7fa16c661a33949459d6e64b1 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -356,6 +356,8 @@ component("ash") {
     "common/system/tray/system_tray.h",
     "common/system/tray/system_tray_bubble.cc",
     "common/system/tray/system_tray_bubble.h",
+    "common/system/tray/system_tray_controller.cc",
+    "common/system/tray/system_tray_controller.h",
     "common/system/tray/system_tray_delegate.cc",
     "common/system/tray/system_tray_delegate.h",
     "common/system/tray/system_tray_item.cc",
@@ -823,6 +825,8 @@ component("ash") {
   ]
   deps = [
     "//ash/autoclick/common:autoclick",
+    # TODO: Why does this cause a cycle? ugh, typemap for shelf item types
+    "//ash/public/interfaces",
     "//ash/touch_hud",
     "//base",
     "//base:i18n",
@@ -835,6 +839,8 @@ component("ash") {
     "//components/wallpaper",
     "//media",
     "//net",
+    # TODO: public_deps?
+    "//services/shell/public/cpp",
     "//skia",
     "//third_party/icu",
     "//ui/accessibility",