Remove use_ash from BUILD.gn in //chrome/browser

We have not shipped Windows Ash for years. There is a 1:1 mapping
between use_ash and is_chromeos, so consolidate them.

Bug: 673826
Test: compiles, gn check for Chrome OS, Linux, Linux Ozone
Change-Id: Idc459cbca6b8447ce0f7e7aa9772e38835492234
Reviewed-on: https://chromium-review.googlesource.com/702756Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506835}

chrome/browser/BUILD.gn

@@ -2693,6 +2693,8 @@ split_static_library("browser") {
       "media/public_session_media_access_handler.h",
       "media/public_session_tab_capture_access_handler.cc",
       "media/public_session_tab_capture_access_handler.h",
+      "media/webrtc/desktop_media_list_ash.cc",
+      "media/webrtc/desktop_media_list_ash.h",
       "memory/memory_kills_histogram.h",
       "memory/memory_kills_monitor.cc",
       "memory/memory_kills_monitor.h",
@@ -2712,12 +2714,21 @@ split_static_library("browser") {
       "metrics/perf/windowed_incognito_observer.h",
       "policy/default_geolocation_policy_handler.cc",
       "policy/default_geolocation_policy_handler.h",
+      "signin/signin_error_notifier_ash.cc",
+      "signin/signin_error_notifier_ash.h",
+      "signin/signin_error_notifier_factory_ash.cc",
+      "signin/signin_error_notifier_factory_ash.h",
+      "sync/sync_error_notifier_ash.cc",
+      "sync/sync_error_notifier_ash.h",
+      "sync/sync_error_notifier_factory_ash.cc",
+      "sync/sync_error_notifier_factory_ash.h",
       "task_manager/providers/arc/arc_process_task.cc",
       "task_manager/providers/arc/arc_process_task.h",
       "task_manager/providers/arc/arc_process_task_provider.cc",
       "task_manager/providers/arc/arc_process_task_provider.h",
     ]
     deps += [
+      "//ash",
       "//chrome/browser/chromeos",
       "//services/ui/public/cpp/input_devices",
       "//services/ui/public/cpp/input_devices:input_device_controller",
@@ -3034,23 +3045,6 @@ split_static_library("browser") {
     deps += [ "//ui/views" ]
   }
 
-  if (use_ash) {
-    # Cross-platform Ash sources.
-    sources += [
-      "media/webrtc/desktop_media_list_ash.cc",
-      "media/webrtc/desktop_media_list_ash.h",
-      "signin/signin_error_notifier_ash.cc",
-      "signin/signin_error_notifier_ash.h",
-      "signin/signin_error_notifier_factory_ash.cc",
-      "signin/signin_error_notifier_factory_ash.h",
-      "sync/sync_error_notifier_ash.cc",
-      "sync/sync_error_notifier_ash.h",
-      "sync/sync_error_notifier_factory_ash.cc",
-      "sync/sync_error_notifier_factory_ash.h",
-    ]
-    deps += [ "//ash" ]
-  }
-
   if (use_aura) {
     # Cross-platform Aura files.
     sources += [

chrome/browser/extensions/BUILD.gn

@@ -970,6 +970,8 @@ static_library("extensions") {
       configs += [ "//build/config/linux/dbus" ]
     }
     deps += [
+      "//ash",
+      "//ash/public/cpp:ash_public_cpp",
       "//components/arc",
       "//components/chrome_apps",
       "//components/constrained_window",
@@ -1134,13 +1136,6 @@ static_library("extensions") {
     deps += [ "//ui/views" ]
   }
 
-  if (use_ash) {
-    deps += [
-      "//ash",
-      "//ash/public/cpp:ash_public_cpp",
-    ]
-  }
-
   if (use_aura) {
     deps += [
       "//ui/aura",