[nplb] Increase max pending buffers in resampler (#752)

Increase kMaximumPendingBuffers in InterleavedSincResampler to fix failed
partial audio tests.

b/274020873
b/289102877

(cherry picked from commit 4a0aee2)

starboard/shared/starboard/player/filter/interleaved_sinc_resampler.cc

@@ -235,6 +235,9 @@ void InterleavedSincResampler::Flush() {
 }
 
 bool InterleavedSincResampler::CanQueueBuffer() const {
+  // TODO(b/289102877): after support partial audio, each input buffer could
+  // have a small amount of frames. We should avoid using count of pending
+  // buffer here.
   if (pending_buffers_.empty()) {
     return true;
   }

starboard/shared/starboard/player/filter/interleaved_sinc_resampler.h

@@ -109,7 +109,7 @@ class InterleavedSincResampler {
   static const int kBufferSize = kBlockSize + kKernelSize;
 
   // The maximum numbers of buffer can be queued.
-  static const int kMaximumPendingBuffers = 8;
+  static const int kMaximumPendingBuffers = 16;
 
   static const int kMaxChannels = 8;
   static const int kInputBufferSize = kMaxChannels * kBufferSize;