Merge TextEditKeyBindingsDelegateAuraLinux into LinuxUi

This CL also adds "assert(is_linux)" to //ui/linux/BUILD.gn

R=sky

Bug: 1317782
Change-Id: Id8c2423de1181609f3e2f1332f36b41bf6676e28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3764706
Reviewed-by: Camille Lamy <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Thomas Anderson <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1026328}
diff --git a/ui/linux/BUILD.gn b/ui/linux/BUILD.gn
index 759d8d0..f290fe3a 100644
--- a/ui/linux/BUILD.gn
+++ b/ui/linux/BUILD.gn
@@ -5,6 +5,8 @@
 import("//build/config/linux/gtk/gtk.gni")
 import("//ui/qt/qt.gni")
 
+assert(is_linux)
+
 component("linux_ui") {
   defines = [ "IS_LINUX_UI_IMPL" ]
   public = [
@@ -57,3 +59,19 @@
     deps += [ "//ui/qt" ]
   }
 }
+
+source_set("test_support") {
+  testonly = true
+
+  public = [ "fake_linux_ui.h" ]
+  sources = [ "fake_linux_ui.cc" ]
+
+  public_deps = [ ":linux_ui" ]
+  deps = [
+    "//base",
+    "//skia",
+    "//ui/gfx",
+    "//ui/native_theme",
+    "//ui/shell_dialogs",
+  ]
+}