Fix grabbing capture when the mouse is pressed on Desktop Linux.

ui/events/devices/x11/device_data_manager_x11.h

Index: ui/events/devices/x11/device_data_manager_x11.h
diff --git a/ui/events/devices/x11/device_data_manager_x11.h b/ui/events/devices/x11/device_data_manager_x11.h
index ec580cbd4ddc77fbc51c22771f63e3e9a7fb175f..bb5fa15d6076c551ce99a61bcf1e4e734c27b7cb 100644
--- a/ui/events/devices/x11/device_data_manager_x11.h
+++ b/ui/events/devices/x11/device_data_manager_x11.h
@@ -239,6 +239,10 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // Returns true if |native_event| should be blocked.
   bool IsEventBlocked(const base::NativeEvent& native_event);
 
+  const std::vector<int>& master_pointers() const {
+    return master_pointers_;
+  }
+
  protected:
   // DeviceHotplugEventObserver:
   void OnKeyboardDevicesUpdated(
@@ -274,6 +278,9 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   std::bitset<kMaxDeviceNum> cmt_devices_;
   std::bitset<kMaxDeviceNum> touchpads_;
 
+  // List of the master pointer devices.
+  std::vector<int> master_pointers_;
+
   // A quick lookup table for determining if events from the XI device
   // should be blocked.
   std::bitset<kMaxDeviceNum> blocked_devices_;