Add hcm@ to public API owners

BUG=skia:
NOTRY=true

Change-Id: I4d54591db0d50ceca02a87868fd125309bd4531e
Reviewed-on: https://skia-review.googlesource.com/7275
Commit-Queue: Ravi Mistry <rmistry@google.com>
Reviewed-by: Mike Reed <reed@google.com>

PRESUBMIT.py

@@ -31,6 +31,8 @@ PUBLIC_API_OWNERS = (
     'bsalomon@google.com',
     'djsollen@chromium.org',
     'djsollen@google.com',
+    'hcm@chromium.org',
+    'hcm@google.com',
 )
 
 AUTHORS_FILE_NAME = 'AUTHORS'