Bug 815643 - Part 4: Add the Convolution processing implementation to the build system; r=roc
Bug 815643 - Part 5: Implement ConvolverNode's processing based on the Blink implementation; r=roc
Bug 815643 - Part 6: Optimize FFTFrame to avoid recreating kiss_fftr_cfg objects all the time; r=roc

Setting up the FFT tables turns out to be quite expensive because of the
large number of calls to sin() and cos().

In the future we may want to look into having a global cache of FFT
tables per size, in order to pay the cost of setting each one of them up
only once.
Bug 815643 - Part 7: Add a basic API test for ConvolverNode; r=roc
Bug 815643 - Part 8: Import convolution tests from Blink; r=roc

Imported from Blink SVN revision 150518
Bug 815643 - Part 9: Port Blink's LayoutTest for ConvolverNode to mochitest-plain; r=roc