Weird, this is the second time the test timed out on Mac10.12 recently (last time was  issue 846188 ).

This idlharness test seems to be much slower than most others. For example, on my powerful Linux workstation (our Mac10.12 bot is much slower):

external/wpt/webaudio/idlharness.https.html takes ~4 seconds on average
external/wpt/WebCryptoAPI/idlharness.https.html takes ~0.5 second on average
external/wpt/generic-sensor/idlharness.https.html takes ~0.5 second on average
...

In fact, most idlharness tests take <1 second. Does webaudio simply have too many interfaces to test?

cc Luke who recently spends a lot of time on IDL testing

FWIW, it takes 2 sec on my Z840 machine running Linux.

https://chromium-review.googlesource.com/c/chromium/src/+/1095640 should theoretically speed it up, but I speculate it would be a teensy/negligible amount, so I've added a long timeout too. It's the quantity of add_idl_objects that makes it so slow compared to similar IDL tests.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/749bef9424276080373b17d54e54ab6956780517

commit 749bef9424276080373b17d54e54ab6956780517
Author: Luke Bjerring <lukebjerring@chromium.org>
Date: Thu Jun 14 12:43:37 2018

Clean up the webaudio idl test and add long timeout

Bug:  851320 
Change-Id: I562fe492be73b0ad8929d8ae8be158230103157f
Reviewed-on: https://chromium-review.googlesource.com/1095640
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Luke Bj <lukebjerring@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567231}
[modify] https://crrev.com/749bef9424276080373b17d54e54ab6956780517/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https-expected.txt
[modify] https://crrev.com/749bef9424276080373b17d54e54ab6956780517/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https.html