Linux: Add xcb FD to glib event loop

build/config/linux/BUILD.gn

Index: build/config/linux/BUILD.gn
diff --git a/build/config/linux/BUILD.gn b/build/config/linux/BUILD.gn
index c6867670026ad69f562e91b0f13ac3fc18b89113..d8ae8e6a016ec60757dbd92fd359a15ddf512a51 100644
--- a/build/config/linux/BUILD.gn
+++ b/build/config/linux/BUILD.gn
@@ -37,6 +37,8 @@ config("fontconfig") {
 config("x11") {
   libs = [
     "X11",
+    "X11-xcb",
+    "xcb",
     "Xcomposite",
     "Xcursor",
     "Xdamage",
@@ -48,6 +50,14 @@ config("x11") {
   ]
 }
 
+config("x11-xcb") {
+  libs = [ "X11-xcb" ]
+}
+
+config("xcb") {
+  libs = [ "xcb" ]
+}
+
 config("xcomposite") {
   libs = [ "Xcomposite" ]
 }