Windows build fix: Only depend on views_bridge_mac in mac builds

views_bridge_mac now uses a function called CreateWindow which happens
to be a macro in Win32 APIs. If a Windows builds sees that function
and knows about the macro, the build breaks, as just happened in
jumbo builds after
https://chromium-review.googlesource.com/c/chromium/src/+/1226251

TBR=ellyjones@chromium.org

Bug: 859152
Change-Id: Ia2314b7697aa75f8df60310cc504848b86c3ed05
Reviewed-on: https://chromium-review.googlesource.com/1229675Reviewed-by: Daniel Bratell <bratell@opera.com>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#591986}

ui/views/BUILD.gn

@@ -513,7 +513,6 @@ jumbo_component("views") {
     "//ui/gfx/animation",
     "//ui/gfx/geometry",
     "//ui/views/resources",
-    "//ui/views_bridge_mac:mojo",
   ]
 
   if (use_x11) {
@@ -742,6 +741,7 @@ jumbo_component("views") {
       "//ui/accelerated_widget_mac",
       "//ui/events:dom_keycode_converter",
     ]
+    public_deps += [ "//ui/views_bridge_mac:mojo" ]
     libs = [
       "AppKit.framework",
       "CoreGraphics.framework",

ui/views_bridge_mac/BUILD.gn

@@ -6,6 +6,7 @@ import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("mojo") {
   cpp_only = true
+  assert(is_mac)
 
   sources = [
     "mojo/bridge_factory.mojom",