Add special case handling for disconnected BiquadFilter.

Add special case handling for disconnected BiquadFilter.

Biquad filters have a tail where zero input can produce non-zero
output due memory from previous inputs.  However, we were
disconnecting biquad filter nodes when the input is disconnected such
as when a source node is finished.  This causes the biquad to suddenly
produce zero output.

Add a case to handle biquad filters like convolver nodes and delay
nodes which don't disconnect their outputs even if the inputs are
disconnected.

This is a temporary solution until full tail-time supported is implemented.
That will fix this issue, and also allow biquad's to be collected when
no longer needed.  With this change, biquad's will be active for a
very long time even with no inputs.

BUG=521155
TEST=biquad-tail.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200691

[Raymond Toy, 2015-08-17 20:05:08]

rtoy@chromium.org changed reviewers:
+ hongchan@chromium.org

[Raymond Toy, 2015-08-17 20:05:09]

PTAL.

[hongchan, 2015-08-17 20:25:40]

LGTM with nits.

https://codereview.chromium.org/1285073005/diff/20001/LayoutTests/webaudio/bi...
File LayoutTests/webaudio/biquad-tail.html (right):

https://codereview.chromium.org/1285073005/diff/20001/LayoutTests/webaudio/bi...
LayoutTests/webaudio/biquad-tail.html:64: successfullyParsed = true;   
</script>
Nit: Need a line break before the script tag.

https://codereview.chromium.org/1285073005/diff/20001/Source/modules/webaudio...
File Source/modules/webaudio/AudioNode.cpp (right):

https://codereview.chromium.org/1285073005/diff/20001/Source/modules/webaudio...
Source/modules/webaudio/AudioNode.cpp:415: // FIXME: we special case the
convolver, delay, and biquad since they have a significant
While we're at this, it would be better for us to use // TODO(rtoy || hongchan)
for this comment.

[Raymond Toy, 2015-08-17 20:44:59]

https://codereview.chromium.org/1285073005/diff/20001/LayoutTests/webaudio/bi...
File LayoutTests/webaudio/biquad-tail.html (right):

https://codereview.chromium.org/1285073005/diff/20001/LayoutTests/webaudio/bi...
LayoutTests/webaudio/biquad-tail.html:64: successfullyParsed = true;   
</script>
On 2015/08/17 20:25:40, hoch wrote:
> Nit: Need a line break before the script tag.

Done.

https://codereview.chromium.org/1285073005/diff/20001/Source/modules/webaudio...
File Source/modules/webaudio/AudioNode.cpp (right):

https://codereview.chromium.org/1285073005/diff/20001/Source/modules/webaudio...
Source/modules/webaudio/AudioNode.cpp:415: // FIXME: we special case the
convolver, delay, and biquad since they have a significant
On 2015/08/17 20:25:40, hoch wrote:
> While we're at this, it would be better for us to use // TODO(rtoy ||
hongchan)
> for this comment.

Done.

[Raymond Toy, 2015-08-17 20:46:51]

The CQ bit was checked by rtoy@chromium.org

[Raymond Toy, 2015-08-17 20:46:51]

The patchset sent to the CQ was uploaded after l-g-t-m from
hongchan@chromium.org
Link to the patchset: https://codereview.chromium.org/1285073005/#ps40001
(title: "Update according to review.")

[commit-bot: I haz the power, 2015-08-17 20:47:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1285073005/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1285073005/40001

[commit-bot: I haz the power, 2015-08-17 22:01:09]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-17 22:01:10]

Try jobs failed on following builders:
  win_chromium_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[Raymond Toy, 2015-08-17 22:33:41]

The CQ bit was checked by rtoy@chromium.org

[Raymond Toy, 2015-08-17 22:33:41]

The patchset sent to the CQ was uploaded after l-g-t-m from
hongchan@chromium.org
Link to the patchset: https://codereview.chromium.org/1285073005/#ps60001
(title: "Fix typo in expected results.")

[commit-bot: I haz the power, 2015-08-17 22:33:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1285073005/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1285073005/60001

[commit-bot: I haz the power, 2015-08-18 01:06:21]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-18 01:06:23]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Raymond Toy, 2015-08-18 02:52:47]

The CQ bit was checked by rtoy@chromium.org

[commit-bot: I haz the power, 2015-08-18 02:53:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1285073005/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1285073005/60001

[commit-bot: I haz the power, 2015-08-18 04:31:55]

Committed patchset #4 (id:60001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200691