Switch from a DataPipe per DecoderBuffer to a single one.
Instead of letting the type converter for DecoderBuffer handle
transfer of the DecoderBuffer::data(), clients are now expected
to handle this externally.
MojoDemuxerStreamAdapter now deserializing the data section via
a shared pipe created by MojoDemuxerStreamImpl. The pipe is
sized dynamically for audio or video content.
We don't have framed DataPipe support yet, but this will at least
prevent us from creating thousands of DataPipes per minute.
BUG=392236
TEST=html_viewer using audio/video urls.
Review URL: https://codereview.chromium.org/
760523008
Cr-Commit-Position: refs/heads/master@{#307328}