Convert //ui to not depend on set_sources_assignment_filter()

set_sources_assignment_filter() is considered as a mis-feature
of gn (as it makes it difficult to reason about the BUILD.gn
files individually).

Convert BUILD.gn files below //ui to instead use conditional
to include source files only on the platformn where they are
used.

The conversion was done by using a modified version of gn that
display all files filtered by set_sources_assignment_filter()
and updating the BUILD.gn files manually to explicitly add the
source files only on the platform that used them.

This CL was uploaded by git cl split.

Bug: 1018739
Change-Id: I0f1dfb9fafe99d71dd45485d9f822acfaee489a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930897Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718585}

ui/events/devices/BUILD.gn

@@ -9,23 +9,23 @@ if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
+# Reset sources_assignment_filter for the BUILD.gn file to prevent
+# regression during the migration of Chromium away from the feature.
+# See build/no_sources_assignment_filter.md for more information.
+# TODO(crbug.com/1018739): remove this when migration is done.
+set_sources_assignment_filter([])
+
 jumbo_component("devices") {
   sources = [
     "device_data_manager.cc",
     "device_data_manager.h",
     "device_hotplug_event_observer.h",
-    "device_util_linux.cc",
-    "device_util_linux.h",
     "events_devices_export.h",
     "gamepad_device.cc",
     "gamepad_device.h",
     "input_device.cc",
     "input_device.h",
     "input_device_event_observer.h",
-    "input_device_observer_android.cc",
-    "input_device_observer_android.h",
-    "input_device_observer_win.cc",
-    "input_device_observer_win.h",
     "stylus_state.h",
     "touch_device_transform.cc",
     "touch_device_transform.h",
@@ -33,6 +33,27 @@ jumbo_component("devices") {
     "touchscreen_device.h",
   ]
 
+  if (is_linux) {
+    sources += [
+      "device_util_linux.cc",
+      "device_util_linux.h",
+    ]
+  }
+
+  if (is_android) {
+    sources += [
+      "input_device_observer_android.cc",
+      "input_device_observer_android.h",
+    ]
+  }
+
+  if (is_win) {
+    sources += [
+      "input_device_observer_win.cc",
+      "input_device_observer_win.h",
+    ]
+  }
+
   defines = [ "EVENTS_DEVICES_IMPLEMENTATION" ]
 
   public_deps = [