EXO: Conditionally build ChromeOS Wayland protocols

Moved protocols under is_chromeos for selective compilation. These
protocols have ChromeOS dependencies and would not compile on other
platforms. This is needed for eventual compilation of exo on Chromecast.

Bug: 896710
Test: Run exo_unittests
Change-Id: Id30ebdc8bf8338cba9e21a87350ab206b6d6057c
Reviewed-on: https://chromium-review.googlesource.com/c/1328566Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611729}

components/exo/wayland/BUILD.gn

@@ -41,16 +41,22 @@ source_set("wayland") {
     "wayland_display_output.h",
     "wayland_input_delegate.cc",
     "wayland_input_delegate.h",
-    "wayland_keyboard_delegate.cc",
-    "wayland_keyboard_delegate.h",
-    "wayland_pointer_delegate.cc",
-    "wayland_pointer_delegate.h",
     "wayland_touch_delegate.cc",
     "wayland_touch_delegate.h",
     "wl_output.cc",
     "wl_output.h",
     "wl_seat.cc",
     "wl_seat.h",
+  ]
+
+  defines = [ "EXO_IMPLEMENTATION" ]
+
+  if (is_chromeos) {
+    sources += [
+      "wayland_keyboard_delegate.cc",
+      "wayland_keyboard_delegate.h",
+      "wayland_pointer_delegate.cc",
+      "wayland_pointer_delegate.h",
       "wl_shell.cc",
       "wl_shell.h",
       "zaura_shell.cc",
@@ -78,8 +84,7 @@ source_set("wayland") {
       "zxdg_shell.cc",
       "zxdg_shell.h",
     ]
-
-  defines = [ "EXO_IMPLEMENTATION" ]
+  }
 
   deps = [
     "//base",