add erikchen as OWNER to sampling_heap_profiler

Change-Id: I1d4fa87a14e9e37a07e5d5446e2b3379a8b27d28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1958688Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723053}

base/sampling_heap_profiler/OWNERS

 alph@chromium.org
+erikchen@chromium.org
 per-file module_cache*=wittman@chromium.org