Revert of Change the video color space default.

Revert of Change the video color space default. (patchset #4 id:60001 of https://codereview.chromium.org/1221903003/)

Reason for revert:
Causing official continuous builds to fail with the following:

../../media/cast/sender/h264_vt_encoder_unittest.cc:308:22: error: no matching constructor for initialization of 'media::VideoDecoderConfig'
  VideoDecoderConfig config(kCodecH264, H264PROFILE_MAIN, frame_->format(),
                     ^      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../media/base/video_decoder_config.h:78:3: note: candidate constructor not viable: requires 10 arguments, but 9 were provided
  VideoDecoderConfig(VideoCodec codec,
  ^
../../media/base/video_decoder_config.h:70:20: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 9 were provided
class MEDIA_EXPORT VideoDecoderConfig {
                   ^
../../media/base/video_decoder_config.h:74:3: note: candidate constructor not viable: requires 0 arguments, but 9 were provided
  VideoDecoderConfig();
  ^
1 error generated.

Original issue's description:
> Change the video color space default.
>
> Previously video without color space metadata was assumed to be in
> Rec601. Now the default depends on the kind of playback. Normal src=
> defaults to Rec601 for SD sized video (<720 pixels high), and Rec709 for
> HD. MSE will always default to Rec709. Using a size based heuristic
> doesn't make sense for MSE where it is common for the resolution to
> change mid playback.
>
> This CL doesn't change the meaning of COLOR_SPACE_UNSPECIFIED. Instead,
> it adds a color space field to VideoDecoderConfig, and updates the video
> decoders to use this as the default if they don't find a more
> authoritative value in the bitstream.
>
> This also fixes a (year old!) bug causing the blackwhite
> tests to always succeed, renames the rec709 blackwhite test
> file to match the name in blackwhite.html, and re-encodes it
> to contain the color space metadata (previously it had none).
>
> BUG=333619
>
> Committed: https://crrev.com/4dc6c2ad0e595a5e0b543e8e1b8961ee0d742a32
> Cr-Commit-Position: refs/heads/master@{#338110}

TBR=dalecurtis@chromium.org,bbudge@chromium.org,codebythepound@gmail.com,gunsch@chromium.org,lcwu@chromium.org,watk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=333619
Committed: https://crrev.com/e735fb0c4b13b72561b8f9931a8788e97deced33
Cr-Commit-Position: refs/heads/master@{#338124}

[amineer_google, 2015-07-09 20:17:09]

Created Revert of Change the video color space default.

[commit-bot: I haz the power, 2015-07-09 20:18:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1228843003/1

[commit-bot: I haz the power, 2015-07-09 20:20:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-09 20:21:35]

Patchset 1 (id:??) landed as
https://crrev.com/e735fb0c4b13b72561b8f9931a8788e97deced33
Cr-Commit-Position: refs/heads/master@{#338124}