use_concatenated_impulse_responses required for grit
use_concatenated_impulse_responses required for grit

If use_concatenated_impulse_responses is set (in config.gni), then
grit needs to have it defined as well.  This is needed to reference
the appropriate response files for the HRTF panner in WebAudio.

BUG=528424
TEST=webaudio panner tests pass

Review URL: https://codereview.chromium.org/1311013010

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#347534}

Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk