Seeing crashes likely from negative touch indexes, check for them

ui/events/ozone/evdev/touch_event_converter_evdev.h

 // Copyright 2014 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.
 
 #ifndef UI_EVENTS_OZONE_EVDEV_TOUCH_EVENT_CONVERTER_EVDEV_H_
 #define UI_EVENTS_OZONE_EVDEV_TOUCH_EVENT_CONVERTER_EVDEV_H_
 
 #include <bitset>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_pump_libevent.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/ozone/evdev/event_converter_evdev.h"
 #include "ui/events/ozone/evdev/event_device_info.h"
 #include "ui/events/ozone/evdev/events_ozone_evdev_export.h"
 
 namespace ui {
 
 class TouchEvent;
 
 class DeviceEventDispatcherEvdev;
 
 class EVENTS_OZONE_EVDEV_EXPORT TouchEventConverterEvdev
     : public EventConverterEvdev {
  public:
-  enum {
-    MAX_FINGERS = 11
-  };
+  enum { MAX_FINGERS = 20 };
   TouchEventConverterEvdev(int fd,
                            base::FilePath path,
                            int id,
                            InputDeviceType type,
                            DeviceEventDispatcherEvdev* dispatcher);
   ~TouchEventConverterEvdev() override;
 
   // EventConverterEvdev:
   bool HasTouchscreen() const override;
   gfx::Size GetTouchscreenSize() const override;
 
   // Unsafe part of initialization.
   virtual void Initialize(const EventDeviceInfo& info);
 
  private:
   friend class MockTouchEventConverterEvdev;
 
   struct InProgressEvents {
     InProgressEvents();
 
+    bool altered_;
     float x_;
     float y_;
     int id_;  // Device reported "unique" touch point id; -1 means not active
     int finger_;  // "Finger" id starting from 0; -1 means not active
 
     EventType type_;
     float radius_x_;
     float radius_y_;
     float pressure_;
   };
@@ skipping 29 matching lines @@
   float x_num_tuxels_;
 
   // Input range for y-axis.
   float y_min_tuxels_;
   float y_num_tuxels_;
 
   // Size of the touchscreen as reported by the driver.
   gfx::Size native_size_;
 
   // Touch point currently being updated from the /dev/input/event* stream.
-  int current_slot_;
-
-  // Bit field tracking which in-progress touch points have been modified
-  // without a syn event.
-  std::bitset<MAX_FINGERS> altered_slots_;
+  size_t current_slot_;
 
   // In-progress touch points.
-  InProgressEvents events_[MAX_FINGERS];
+  std::vector<InProgressEvents> events_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventConverterEvdev);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_OZONE_EVDEV_TOUCH_EVENT_CONVERTER_EVDEV_H_