MediaStreamRecorder: implement requestData() and start(timeslice)

This CL implements requestData() [1] and a fast LayoutTest.
requestData() forces sending the gathered data so-far to JS.
Until now there's no buffering, so this part just resends the
last gathered Blob, so there will be more patches dealing
with the behaviour for buffered MSRs.

This CL also implements the start(timeslice) [2], essentially
Chrome uses the |lastInSlice| parameter to instruct Blink to
finish buffering data and send to JS.

[1] http://w3c.github.io/mediacapture-record/MediaRecorder.html#widl-MediaRecorder-requestData-void
[2] http://w3c.github.io/mediacapture-record/MediaRecorder.html#widl-MediaRecorder-start-void-long-timeslice

BUG=543838, 543828
TBR=dalecurtis@chromium.org for media/capture/webm_muxer.cc
where I indented one line (no need for review, no new code).

Review URL: https://codereview.chromium.org/1420133003

Cr-Commit-Position: refs/heads/master@{#356207}

1 files changed, 2 insertions, 2 deletions

diff --git a/media/capture/webm_muxer.cc b/media/capture/webm_muxer.cc
index a2285ef..31dfade 100644
--- a/media/capture/webm_muxer.cc
+++ b/media/capture/webm_muxer.cc
@@ -103,8 +103,8 @@ void WebmMuxer::AddVideoTrack(const gfx::Size& frame_size, double frame_rate) {
 mkvmuxer::int32 WebmMuxer::Write(const void* buf, mkvmuxer::uint32 len) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(buf);
-  write_data_callback_.Run(base::StringPiece(reinterpret_cast<const char*>(buf),
-                                            len));
+  write_data_callback_.Run(
+      base::StringPiece(reinterpret_cast<const char*>(buf), len));
   position_ += len;
   return 0;
 }