Protect AudioRendererAlgorithm from invalid step sizes.

BUG=165430
TEST=unittests and asan pass.

Review URL: https://codereview.chromium.org/11573023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@173249 0039d316-1c4b-4281-b951-d872f2087c98
AudioRendererAlgorithm::AudioRendererAlgorithm()
    : channels_(0),
      samples_per_second_(0),
      bytes_per_channel_(0),
      playback_rate_(0.0f),
      audio_buffer_(0, kStartingBufferSizeInBytes),
      bytes_in_crossfade_(0),
      bytes_per_frame_(0),
      index_into_window_(0),
      crossfade_frame_number_(0),
      muted_(false),
      needs_more_data_(false),
      window_size_(0) {
}

AudioRendererAlgorithm::AudioRendererAlgorithm()
    : channels_(0),
      samples_per_second_(0),
      bytes_per_channel_(0),
      playback_rate_(0.0f),
      audio_buffer_(0, kStartingBufferSizeInBytes),
      bytes_in_crossfade_(0),
      bytes_per_frame_(0),
      index_into_window_(0),
      crossfade_frame_number_(0),
      muted_(false),
      needs_more_data_(false),
      window_size_(0) {
}
