Implement a runtime headless mode for Linux

content/gpu/gpu_main.cc

Index: content/gpu/gpu_main.cc
diff --git a/content/gpu/gpu_main.cc b/content/gpu/gpu_main.cc
index a529db776818dba3ba9a39c0baf9ff2ca58d5c60..00c21c825ff7453ab7880a706cdfff55240b8988 100644
--- a/content/gpu/gpu_main.cc
+++ b/content/gpu/gpu_main.cc
@@ -40,6 +40,7 @@
 #include "gpu/ipc/service/gpu_memory_buffer_factory.h"
 #include "gpu/ipc/service/gpu_watchdog_thread.h"
 #include "ui/events/platform/platform_event_source.h"
+#include "ui/gfx/switches.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface.h"
@@ -200,35 +201,39 @@ int GpuMain(const MainFunctionParams& parameters) {
   // TODO(ericrk): Revisit this once we assess its impact on crbug.com/662802
   // and crbug.com/609252.
   std::unique_ptr<base::MessageLoop> main_message_loop;
-
+  if (command_line.HasSwitch(switches::kHeadless)) {
+    main_message_loop.reset(
+        new base::MessageLoop(base::MessageLoop::TYPE_DEFAULT));
+  } else {
 #if defined(OS_WIN)
-  // OK to use default non-UI message loop because all GPU windows run on
-  // dedicated thread.
-  main_message_loop.reset(
-      new base::MessageLoop(base::MessageLoop::TYPE_DEFAULT));
+    // OK to use default non-UI message loop because all GPU windows run on
+    // dedicated thread.
+    main_message_loop.reset(
+        new base::MessageLoop(base::MessageLoop::TYPE_DEFAULT));
 #elif defined(USE_X11)
-  // We need a UI loop so that we can grab the Expose events. See GLSurfaceGLX
-  // and https://crbug.com/326995.
-  main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_UI));
-  std::unique_ptr<ui::PlatformEventSource> event_source =
-      ui::PlatformEventSource::CreateDefault();
+    // We need a UI loop so that we can grab the Expose events. See GLSurfaceGLX
+    // and https://crbug.com/326995.
+    main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_UI));
+    std::unique_ptr<ui::PlatformEventSource> event_source =
+        ui::PlatformEventSource::CreateDefault();
 #elif defined(USE_OZONE) && defined(OZONE_X11)
-  // If we might be running Ozone X11 we need a UI loop to grab Expose events.
-  // See GLSurfaceGLX and https://crbug.com/326995.
-  main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_UI));
+    // If we might be running Ozone X11 we need a UI loop to grab Expose events.
+    // See GLSurfaceGLX and https://crbug.com/326995.
+    main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_UI));
 #elif defined(USE_OZONE)
-  main_message_loop.reset(
-      new base::MessageLoop(base::MessageLoop::TYPE_DEFAULT));
+    main_message_loop.reset(
+        new base::MessageLoop(base::MessageLoop::TYPE_DEFAULT));
 #elif defined(OS_LINUX)
 #error "Unsupported Linux platform."
 #elif defined(OS_MACOSX)
-  // This is necessary for CoreAnimation layers hosted in the GPU process to be
-  // drawn. See http://crbug.com/312462.
-  std::unique_ptr<base::MessagePump> pump(new base::MessagePumpCFRunLoop());
-  main_message_loop.reset(new base::MessageLoop(std::move(pump)));
+    // This is necessary for CoreAnimation layers hosted in the GPU process to
+    // be drawn. See http://crbug.com/312462.
+    std::unique_ptr<base::MessagePump> pump(new base::MessagePumpCFRunLoop());
+    main_message_loop.reset(new base::MessageLoop(std::move(pump)));
 #else
-  main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_IO));
+    main_message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_IO));
 #endif
+  }
 
   base::PlatformThread::SetName("CrGpuMain");