Seeing crashes likely from negative touch indexes, check for them

ui/events/ozone/evdev/touch_event_converter_evdev_unittest.cc

 // 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.
 
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/input.h>
 #include <unistd.h>
 
 #include <vector>
@@ skipping 102 matching lines @@
 
   if (pipe(fds))
     PLOG(FATAL) << "failed pipe";
 
   DCHECK(SetNonBlocking(fds[0]) == 0)
       << "SetNonBlocking for pipe fd[0] failed, errno: " << errno;
   DCHECK(SetNonBlocking(fds[1]) == 0)
       << "SetNonBlocking for pipe fd[0] failed, errno: " << errno;
   read_pipe_ = fds[0];
   write_pipe_ = fds[1];
+
+  events_.resize(MAX_FINGERS);
 }
 
 void MockTouchEventConverterEvdev::ConfigureReadMock(struct input_event* queue,
                                                      long read_this_many,
                                                      long queue_index) {
   int nwrite = HANDLE_EINTR(write(write_pipe_,
                                   queue + queue_index,
                                   sizeof(struct input_event) * read_this_many));
   DCHECK(nwrite ==
          static_cast<int>(sizeof(struct input_event) * read_this_many))
@@ skipping 431 matching lines @@
       {{0, 0}, EV_ABS, ABS_MT_POSITION_X, 777},
       {{0, 0}, EV_ABS, ABS_MT_POSITION_Y, 666},
       {{0, 0}, EV_SYN, SYN_REPORT, 0},
   };
 
   // Check that one 1 event is generated
   dev->ConfigureReadMock(mock_kernel_queue, arraysize(mock_kernel_queue), 0);
   dev->ReadNow();
   EXPECT_EQ(1u, size());
 }