Do not create the NativeViewport PlatformEventSource when headless.

components/native_viewport/native_viewport_application_delegate.cc

Index: components/native_viewport/native_viewport_application_delegate.cc
diff --git a/components/native_viewport/native_viewport_application_delegate.cc b/components/native_viewport/native_viewport_application_delegate.cc
index 63eff6bd5c512df3bb8563f4997f37c3fa737c45..f77a944efef1a27f5ab982c06ed2a89da28cdd65 100644
--- a/components/native_viewport/native_viewport_application_delegate.cc
+++ b/components/native_viewport/native_viewport_application_delegate.cc
@@ -24,12 +24,12 @@ NativeViewportApplicationDelegate::~NativeViewportApplicationDelegate() {
 
 void NativeViewportApplicationDelegate::Initialize(
     mojo::ApplicationImpl* application) {
-  event_source_ = ui::PlatformEventSource::CreateDefault();
   tracing_.Initialize(application);
 
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   is_headless_ = command_line->HasSwitch(mojo::kUseHeadlessConfig);
   if (!is_headless_) {
+    event_source_ = ui::PlatformEventSource::CreateDefault();
     if (command_line->HasSwitch(mojo::kUseTestConfig))
       gfx::GLSurface::InitializeOneOffForTests();
     else