Gate support for certain EOTFs/primaries/matrices on color management / hdr flags

Creates a new class VideoColorSpace specifically for encoding color spaces
according to ISO/IEC 23001-8.

Plumb this color space through from parsing to validation.

BUG=687627

Review-Url: https://codereview.chromium.org/2742113002
Cr-Commit-Position: refs/heads/master@{#456518}
bool MimeUtil::IsSupportedMediaMimeType(const std::string& mime_type) const {
  return media_format_map_.find(base::ToLowerASCII(mime_type)) !=
         media_format_map_.end();
}

bool MimeUtil::IsSupportedMediaMimeType(const std::string& mime_type) const {
  return media_format_map_.find(base::ToLowerASCII(mime_type)) !=
         media_format_map_.end();
}
