Implement a runtime headless mode for Linux

ui/base/ime/input_method_factory.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/base/ime/input_method_factory.h"
 
+#include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "build/build_config.h"
 #include "ui/base/ime/mock_input_method.h"
+#include "ui/gfx/switches.h"
 
 #if defined(OS_CHROMEOS)
 #include "ui/base/ime/input_method_chromeos.h"
 #elif defined(OS_WIN)
 #include "ui/base/ime/input_method_win.h"
 #elif defined(OS_MACOSX)
 #include "ui/base/ime/input_method_mac.h"
 #elif defined(USE_AURA) && defined(OS_LINUX) && defined(USE_X11)
 #include "ui/base/ime/input_method_auralinux.h"
 #elif defined(OS_ANDROID)
 #include "ui/base/ime/input_method_android.h"
 #else
 #include "ui/base/ime/input_method_minimal.h"
 #endif
 
 namespace {
 
 ui::InputMethod* g_input_method_for_testing = nullptr;
 
 bool g_input_method_set_for_testing = false;
 
 bool g_create_input_method_called = false;
 
 }  // namespace
 
 namespace ui {
+namespace {
+
+bool RunningInHeadlessMode() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless);
+}
+
+}  // namespace
 
 std::unique_ptr<InputMethod> CreateInputMethod(
     internal::InputMethodDelegate* delegate,
     gfx::AcceleratedWidget widget) {
   if (!g_create_input_method_called)
     g_create_input_method_called = true;
 
   if (g_input_method_for_testing) {
     ui::InputMethod* ret = g_input_method_for_testing;
     g_input_method_for_testing = nullptr;
     return base::WrapUnique(ret);
   }
 
   if (g_input_method_set_for_testing)
     return base::MakeUnique<MockInputMethod>(delegate);
 
+  if (RunningInHeadlessMode())
+    return base::WrapUnique(new MockInputMethod(delegate));
+
 #if defined(OS_CHROMEOS)
   return base::MakeUnique<InputMethodChromeOS>(delegate);
 #elif defined(OS_WIN)
   return base::MakeUnique<InputMethodWin>(delegate, widget);
 #elif defined(OS_MACOSX)
   return base::MakeUnique<InputMethodMac>(delegate);
 #elif defined(USE_AURA) && defined(OS_LINUX) && defined(USE_X11)
   return base::MakeUnique<InputMethodAuraLinux>(delegate);
 #elif defined(OS_ANDROID)
   return base::MakeUnique<InputMethodAndroid>(delegate);
@@ skipping 12 matching lines @@
       << "ui::SetUpInputMethodFactoryForTesting earlier.";
 
   g_input_method_set_for_testing = true;
 }
 
 void SetUpInputMethodForTesting(InputMethod* input_method) {
   g_input_method_for_testing = input_method;
 }
 
 }  // namespace ui