Add myself to content/browser/loader/OWNER

Change-Id: I32178c4171544265f375d555a1203947ede5b1c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1950105Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721872}

content/browser/loader/OWNERS

 csharrison@chromium.org
 mmenke@chromium.org
+toyoshim@chromium.org
 
 # TEAM: net-dev@chromium.org
 # COMPONENT: Internals>Network