title: Getting 'Permission denied (13)' when trying to use systrace on Moto X with KitKat
body: <p>I'm following <a href="http://developer.android.com/tools/debugging/systrace.html">http://developer.android.com/tools/debugging/systrace.html</a> but can't run systrace on my Moto X (KitKat). Any ideas? </p>
  
  <pre><code>$ python systrace.py --time=10 -o mynewtrace.html gfx view wm
  
  
  error opening /sys/kernel/debug/tracing/options/overwrite: Permission denied (13)
  error opening /sys/kernel/debug/tracing/buffer_size_kb: Permission denied (13)
  error opening /sys/kernel/debug/tracing/trace_clock: Permission denied (13)
  error opening /sys/kernel/debug/tracing/tracing_on: Permission denied (13)
  error opening /sys/kernel/debug/tracing/tracing_on: Permission denied (13)
  unable to start tracing
  error opening /sys/kernel/debug/tracing/options/overwrite: Permission denied (13)
  error opening /sys/kernel/debug/tracing/buffer_size_kb: Permission denied (13)
  error opening /sys/kernel/debug/tracing/trace_clock: Permission denied (13)
  No data was captured.  Output file was not written.
  </code></pre>