Correctly handle any number of channels in WebAudio file decoder on Android

Correctly handle any number of channels in WebAudio file decoder on Android.

CopyPcmDataToBus incorrectly assumed that each pipe contained a
integer number of frames.  This is only true if the number of channels
is 1 or 2.  For more channels, this is false, so we have to copy the
data carefully, keeping track of which sample in a frame we are in.

BUG=343648
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=252223

[Raymond Toy (Google), 2014-02-19 17:52:47]

PTAL

[Raymond Toy (Google), 2014-02-19 18:06:36]

PTAL

[qinmin, 2014-02-19 22:48:07]

lgtm

[Raymond Toy (Google), 2014-02-19 22:53:26]

On 2014/02/19 22:48:07, qinmin wrote:
> lgtm

Thanks

[Raymond Toy (Google), 2014-02-19 22:53:49]

The CQ bit was checked by rtoy@google.com

[commit-bot: I haz the power, 2014-02-19 23:19:08]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/164023007/1

[commit-bot: I haz the power, 2014-02-20 01:10:31]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/164023007/1

[commit-bot: I haz the power, 2014-02-20 04:54:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/164023007/1

[commit-bot: I haz the power, 2014-02-20 08:54:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/164023007/1

[commit-bot: I haz the power, 2014-02-20 12:23:15]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/164023007/1

[commit-bot: I haz the power, 2014-02-20 13:43:28]

Change committed as 252223