Content "gn check" work.

content/gpu/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
 import("//content/content.gni")
 import("//media/media_options.gni")
 
 # See //content/BUILD.gn for how this works.
 group("gpu") {
-  visibility = [ "//content/*" ]
+  visibility = [ "//content/*" ]  # This is an internal content API.
 
   if (is_component_build) {
     public_deps = [
       "//content",
     ]
   } else {
     public_deps = [
       ":gpu_sources",
     ]
   }
 }
 
 source_set("gpu_sources") {
+  # This is an internal content API. Code outside of the content "component"
+  # (like content/test and content/shell) should depend on ":gpu" above.
   visibility = [ "//content/*" ]
 
   sources = [
     "gpu_child_thread.cc",
     "gpu_child_thread.h",
     "gpu_main.cc",
     "gpu_process.cc",
     "gpu_process.h",
     "gpu_process_control_impl.cc",
     "gpu_process_control_impl.h",
     "gpu_watchdog_thread.cc",
     "gpu_watchdog_thread.h",
     "in_process_gpu_thread.cc",
     "in_process_gpu_thread.h",
   ]
 
   configs += [ "//content:content_implementation" ]
 
   deps = [
     "//base",
+    "//base/third_party/dynamic_annotations",
+    "//components/tracing",
     "//content:export",
+    "//content/common",
     "//content/public/child:child_sources",
     "//content/public/common:common_sources",
     "//gpu:gpu",
     "//gpu/ipc/common:command_buffer_traits",
     "//ipc",
+    "//media/mojo/services:application_factory",
     "//mojo/shell/public/interfaces",
     "//skia",
+    "//ui/events/ipc",
+    "//ui/gfx/ipc",
     "//ui/gl",
   ]
 
-  public_deps = [
-    "//content/common:mojo_bindings",
-  ]
-
   if (mojo_media_host == "gpu") {
     deps += [ "//media/mojo/services:application_factory" ]
   }
 
   if (is_win) {
     configs += [
       "//third_party/khronos:khronos_headers",
       "//third_party/wtl:wtl_includes",
     ]
     libs = [ "setupapi.lib" ]
     deps += [
+      "//sandbox",
       "//third_party/angle:libEGL",
       "//third_party/angle:libGLESv2",
     ]
   }
 
   if (is_chromeos && current_cpu != "arm") {
     configs += [ "//third_party/libva:libva_config" ]
   }
 
   if (use_x11) {
     deps += [ "//ui/events/platform/x11" ]
   }
 
+  if (use_ozone) {
+    deps += [ "//ui/ozone" ]
+  }
+
   if (enable_vulkan) {
     deps += [ "//gpu/vulkan" ]
   }
 }