Avoid logging certain errors for non main frames.
ERR_IPC_WITH_NO_RELEVANT_LOAD and ERR_IPC_FROM_BAD_URL_SCHEME are
errors that help to understand when we receive messages from a
render process that aren't expected in the browser process.
Historically, we only tracked main frames, so it made sense to
log these on all IPCs.
As of https://codereview.chromium.org/2859393002, we receive
IPCs from both main and child frames.
It is valid and expected to receive these IPCs from a child
frame when we aren't tracking a main frame, as render tracking
policy is purely per frame and has no awareness of the main
frame's URL etc.
Thus, we update the code that logs these errors to only do so
for messages received from main frames.
Comment 1 by bugdroid1@chromium.org
, Jun 22 2017