Add Xorg+dummy as alternative for Xvfb

remoting/host/curtain_mode_linux.cc

Index: remoting/host/curtain_mode_linux.cc
diff --git a/remoting/host/curtain_mode_linux.cc b/remoting/host/curtain_mode_linux.cc
index 05031bfec1b255b300d521dfde30b5686b785fa0..b99ae2dfffd3babb4cf3fd52a27c76dc0b7fa592 100644
--- a/remoting/host/curtain_mode_linux.cc
+++ b/remoting/host/curtain_mode_linux.cc
@@ -23,8 +23,8 @@ class CurtainModeLinux : public CurtainMode {
   bool Activate() override;
 
  private:
-  // Returns true if the host is running under an Xvfb session.
-  bool IsXvfbSession();
+  // Returns true if the host is running under a virtual session.
+  bool IsVirtualSession();
 
   DISALLOW_COPY_AND_ASSIGN(CurtainModeLinux);
 };
@@ -34,25 +34,25 @@ CurtainModeLinux::CurtainModeLinux() {
 
 bool CurtainModeLinux::Activate() {
   // We can't curtain the session in run-time in Linux.
-  // Either the session is running on Xvfb (i.e. always curtained), or it is
-  // attached to the physical console (i.e. impossible to curtain).
-  bool activated = IsXvfbSession();
-  if (!activated) {
-    LOG(ERROR) << "Curtain-mode is not supported when running on non-Xvfb "
+  // Either the session is running in a virtual session (i.e. always curtained),
+  // or it is attached to the physical console (i.e. impossible to curtain).
+  if (!IsVirtualSession()) {
+    LOG(ERROR) << "Curtain-mode is not supported when running on non-virtual "
                   "X server";
+    return false;
   }
 
-  return activated;
+  return true;
 }
 
-bool CurtainModeLinux::IsXvfbSession() {
-  // Try to identify an Xvfb session. There's no way to query what X server we
-  // are running under, so we check for the Xvfb input devices.
+bool CurtainModeLinux::IsVirtualSession() {
+  // Try to identify a virtual session. Since there's no way to tell from the
+  // vendor string, we check for known virtual input devices.
   // TODO(rmsousa): Find a similar way to determine that the *output* is secure.
   Display* display = XOpenDisplay(nullptr);
   int opcode, event, error;
   if (!XQueryExtension(display, "XInputExtension", &opcode, &event, &error)) {
-    // If XInput is not available, assume it is not an Xvfb session.
+    // If XInput is not available, assume it is not a virtual session.
     LOG(ERROR) << "X Input extension not available: " << error;
     XCloseDisplay(display);
     return false;
@@ -61,6 +61,7 @@ bool CurtainModeLinux::IsXvfbSession() {
   XDeviceInfo* devices;
   bool found_xvfb_mouse = false;
   bool found_xvfb_keyboard = false;
+  bool found_crd_void_input = false;
   bool found_other_devices = false;
   devices = XListInputDevices(display, &num_devices);
   for (int i = 0; i < num_devices; i++) {
@@ -68,9 +69,12 @@ bool CurtainModeLinux::IsXvfbSession() {
     if (device_info->use == IsXExtensionPointer) {
       if (strcmp(device_info->name, "Xvfb mouse") == 0) {
         found_xvfb_mouse = true;
+      } else if (strcmp(device_info->name,
+                        "Chrome Remote Desktop Input") == 0) {
+        found_crd_void_input = true;
       } else if (strcmp(device_info->name, "Virtual core XTEST pointer") != 0) {
         found_other_devices = true;
-        HOST_LOG << "Non Xvfb mouse found: " << device_info->name;
+        HOST_LOG << "Non-virtual mouse found: " << device_info->name;
       }
     } else if (device_info->use == IsXExtensionKeyboard) {
       if (strcmp(device_info->name, "Xvfb keyboard") == 0) {
@@ -78,26 +82,27 @@ bool CurtainModeLinux::IsXvfbSession() {
       } else if (strcmp(device_info->name,
                         "Virtual core XTEST keyboard") != 0) {
         found_other_devices = true;
-        HOST_LOG << "Non Xvfb keyboard found: " << device_info->name;
+        HOST_LOG << "Non-virtual keyboard found: " << device_info->name;
       }
     } else if (device_info->use == IsXPointer) {
       if (strcmp(device_info->name, "Virtual core pointer") != 0) {
         found_other_devices = true;
-        HOST_LOG << "Non Xvfb mouse found: " << device_info->name;
+        HOST_LOG << "Non-virtual mouse found: " << device_info->name;
       }
     } else if (device_info->use == IsXKeyboard) {
       if (strcmp(device_info->name, "Virtual core keyboard") != 0) {
         found_other_devices = true;
-        HOST_LOG << "Non Xvfb keyboard found: " << device_info->name;
+        HOST_LOG << "Non-virtual keyboard found: " << device_info->name;
       }
     } else {
       found_other_devices = true;
-      HOST_LOG << "Non Xvfb device found: " << device_info->name;
+      HOST_LOG << "Non-virtual device found: " << device_info->name;
     }
   }
   XFreeDeviceList(devices);
   XCloseDisplay(display);
-  return found_xvfb_mouse && found_xvfb_keyboard && !found_other_devices;
+  return ((found_xvfb_mouse && found_xvfb_keyboard) || found_crd_void_input)
+      && !found_other_devices;
 }
 
 // static