b=939491 avoid producing infinite stream of subnormals in BiquadFilterNode tail r=padenot

Using double precision for the processing means the main loop is unlikely to
encounter subnormals and provides suitable extra precision to minimize
accumulation of error.

If the tail output values are denormalized when converted to single precision
then flush them to zero to reduce downstream computation cost.

--HG--
extra : transplant_source : %08%09u%C48%E3i%AB%23%1B%D8_kz%E5%A8_%3D%C4%93
b=937475 change DURATION from end-offset to duration and compare buffer length using integer sample count r=ehsan

--HG--
extra : transplant_source : %2BS%A0%A1%C04%BC%1D%A7vDh%8E%A4%F7%90%E62%DC%3D
b=937475 separate stream position from buffer position so that stop time can use stream position r=ehsan

--HG--
extra : transplant_source : %8C%F0%05w%0A%C6%21%11%D5A4%85%FD%BC%D6%1F%9A%B8%FE%CB
b=937057 provide a null ptr instead of a zero buffer when processing resampler tail r=padenot

--HG--
extra : transplant_source : %8EK%22q%A6%E9%82%F1%5E-%9E%BEs%01%F1%D1Jj%097
b=938450 process all input samples in decodeAudioData r=padenot

--HG--
extra : transplant_source : %01%B2%FE%DA%BE%2CcX%B9%A7%60%15%FB%08%C5%2AS%99%B28
b=938450 test lengths of decoded audio and change 48k wav files to 48k f=padenot

New wave files differ from those generated from ogg files using sox 14.4.1 and
libvorbis 1.3.3 by being one quantum less on about half of the samples.

--HG--
extra : transplant_source : B%27%8F%2B%40%22%C5%25%0CS%22%28%40%C0%C3%0EM%87%87%A7
b=938450 rename compareBuffers to compareChannels & add compareBuffers f=ehsan

--HG--
extra : transplant_source : %93W%BC%84%FF%10%9B%F5%CD5%98%0E%F0/%F2R%B9W%1E%94
b=938450 reduce the number of offset parameters to compareChannels() f=ehsan

findFirstNonZeroSample() won't return an offset > buffer length, so clamping
the result to <= 2048 is not necessary.

--HG--
extra : transplant_source : %28HV%B3%9A%AA%D6%8C6n%FD%18%AE%D6g%83%03%EA%09%D4
b=938450 load the expected file only once and remove unused monoTest parameter

--HG--
extra : transplant_source : %8C%A4%04%FB%9E%F3%1D%90%DB%C7%B1-e.%1C%08%B7%84%7Fl
b=938450 use an OfflineAudioContext to test decodeAudioData at different sample rates f=padenot

--HG--
extra : transplant_source : %CF.%22r%F8%BB%D7%21%17%E9%96%19y1%5B%D0%E6%F0%D1%18