Update OWNERs for profiling process code.

Adding myself, brettw@ and ajwong@.

Bug: 
Change-Id: I6192ff1b4eefdf400b640e6ea7c61f8c297726a2
Reviewed-on: https://chromium-review.googlesource.com/661380Reviewed-by: Albert J. Wong <ajwong@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501459}

chrome/browser/profiling_host/OWNERS

+ajwong@chromium.org
+brettw@chromium.org
+erikchen@chromium.org

chrome/common/profiling/OWNERS

+ajwong@chromium.org
+brettw@chromium.org
+erikchen@chromium.org
+
 per-file *.mojom=set noparent
 per-file *.mojom=file://ipc/SECURITY_OWNERS

chrome/profiling/OWNERS

+ajwong@chromium.org
+brettw@chromium.org
+erikchen@chromium.org
+
 per-file profiling_manifest.json=set noparent
 per-file profiling_manifest.json=file://ipc/SECURITY_OWNERS