Implement a runtime headless mode for Linux

ui/aura/env.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/env.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_local.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/input_state_lookup.h"
 #include "ui/aura/mus/window_port_mus.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_observer.h"
 #include "ui/aura/window_port_local.h"
 #include "ui/events/event_target_iterator.h"
 #include "ui/events/platform/platform_event_source.h"
+#include "ui/gfx/switches.h"
 
 #if defined(USE_OZONE)
 #include "ui/ozone/public/ozone_platform.h"
 #endif
 
 namespace aura {
 
 namespace {
 
 // Env is thread local so that aura may be used on multiple threads.
 base::LazyInstance<base::ThreadLocalPointer<Env> >::Leaky lazy_tls_ptr =
     LAZY_INSTANCE_INITIALIZER;
 
 // Returns true if running inside of mus. Checks for mojo specific flag.
 bool RunningInsideMus() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       "primordial-pipe-token");
 }
 
+bool RunningInHeadlessMode() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless);
+}
+
 }  // namespace
 
 // Observes destruction and changes of the FocusClient for a window.
 // ActiveFocusClientWindowObserver is created for the window the FocusClient is
 // associated with.
 class Env::ActiveFocusClientWindowObserver : public WindowObserver {
  public:
   explicit ActiveFocusClientWindowObserver(Window* window) : window_(window) {
     window_->AddObserver(this);
   }
@@ skipping 105 matching lines @@
     : mode_(mode),
       mouse_button_flags_(0),
       is_touch_down_(false),
       input_state_lookup_(InputStateLookup::Create()),
       context_factory_(NULL) {
   DCHECK(lazy_tls_ptr.Pointer()->Get() == NULL);
   lazy_tls_ptr.Pointer()->Set(this);
 }
 
 void Env::Init() {
-  if (RunningInsideMus())
+  if (RunningInsideMus() || RunningInHeadlessMode())
     return;
 #if defined(USE_OZONE)
   // The ozone platform can provide its own event source. So initialize the
   // platform before creating the default event source. If running inside mus
   // let the mus process initialize ozone instead.
   ui::OzonePlatform::InitializeForUI();
 #endif
   if (!ui::PlatformEventSource::GetInstance())
     event_source_ = ui::PlatformEventSource::CreateDefault();
 }
@@ skipping 31 matching lines @@
 std::unique_ptr<ui::EventTargetIterator> Env::GetChildIterator() const {
   return nullptr;
 }
 
 ui::EventTargeter* Env::GetEventTargeter() {
   NOTREACHED();
   return NULL;
 }
 
 }  // namespace aura