Update OWNERS in modules/{filesystem,quota}

BUG=n/a
TEST=n/a
NOTRY=true

Review URL: https://codereview.chromium.org/321503003

git-svn-id: svn://svn.chromium.org/blink/trunk@175645 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/modules/filesystem/OWNERS

 ericu@chromium.org
 kinuko@chromium.org
 michaeln@chromium.org
+nhiroki@chromium.org
+tzik@chromium.org

third_party/WebKit/Source/modules/quota/OWNERS

 kinuko@chromium.org
+nhiroki@chromium.org
+tzik@chromium.org