Reland: Implement Aura side of unified touch text selection for contents

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index 8114b7da37c9d2e41a7520b3cc42bab0f77e510e..49707182f10d09eee7d465560dc35f7ded46f02c 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -319,11 +319,6 @@ if (!is_mac) {
 
     data_deps = [ "//ppapi:ppapi_tests" ]  # Loaded at runtime.
 
-    if (!is_chromeos) {
-      sources -=
-          [ "../browser/web_contents/touch_editable_impl_aura_browsertest.cc" ]
-    }
-
     if (is_win) {
       sources += rebase_path(
               content_tests_gypi_values.content_browsertests_win_sources,