Add ash devtools client

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index a47cae7043cde8016cb3263e2847c820d504e309..bd063bc958c28657feedd66d649f40879081852d 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -78,6 +78,8 @@ component("ash") {
     "common/cast_config_delegate.h",
     "common/default_accessibility_delegate.cc",
     "common/default_accessibility_delegate.h",
+    "common/devtools/devtools_dom_agent.cc",
+    "common/devtools/devtools_dom_agent.h",
     "common/drag_drop/drag_image_view.cc",
     "common/drag_drop/drag_image_view.h",
     "common/focus_cycler.cc",
@@ -854,6 +856,7 @@ component("ash") {
     "//components/onc",
     "//components/session_manager:base",
     "//components/signin/core/account_id",
+    "//components/ui_devtools",

[sky, 2016/10/28 21:27:10]

What are all the dependencies of this? I want to make sure we don't end up
pulling in content/blink. How many additional build files do this pull in?

[Sarmad Hashmi, 2016/10/28 21:58:19]

Dependencies are base, net, net:http_server, and an action which generates the
protocol using files from here:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/inspe...

     "//components/user_manager",
     "//components/wallpaper",
     "//media",