b=983066 pad out resampler input past track end only to the end of the block r=padenot

The extra null samples were mostly harmless, and may have even helped avoid
bug 983062 sometimes, but caused the "Samples missing" assertion to fail.

--HG--
extra : transplant_source : M%D6%B4ra2%AE%DA%EC%82%E1%D8_%83%9F%FBw%F2%ECh
crashtest for bug 986901

Derived from testcase by Jesse Ruderman <jruderman@gmail.com>

--HG--
extra : transplant_source : %AE%CEf%29%F9%C4%25%82%B5%17%24%3C%0ErA%90.%7C%09%0C
b=986901 don't assume that DelayNode maxDelayTime is greater than 1 block r=padenot

Also apply DelayNode maxDelayTime before rounding to ticks.

--HG--
extra : transplant_source : %F1i%02%2A%ED%98%95%C9u%60%0B%1A%81A%C2%8E%FB%F3%FA%D5
b=987976 make AudioNodeExternalInputStream output channel count match stream, unless > MaxChannelCount r=padenot

The difference from Blink here is that Blink plays silence for if element
channel counts are > 32, but here more channels are down-mixed.  Media stream
channel counts are also fixed to 2 in Blink, but that restriction is not
applied here.

Leaving the "inline" const static/class member initialization of
MaxChannelCount left missing symbols with gcc 4.7.3.

--HG--
extra : transplant_source : %C9%BA%84%0F%E8%89%E2%85p%B8%28%EF%E9M%CC%81%B9ob/
b=987976 rename ComputeFinalOuputChannelCount ComputedNumberOfChannels to match spec r=padenot

to remove any implication that the function might be for calculating
the number of output channels for an AudioNode.

--HG--
extra : transplant_source : %D9%12%BB%23n%92%EB%F7%1Df%11%3F%04%B4z%606%ADT%3A
b=989907 initialize AudioNodeExternalInputStream output chunk even when first track has null output r=roc

--HG--
extra : transplant_source : %96%C3%A3%DCs%D3%CCY6.%CC%07%22%02%EDy%A5%94U%DD