TimelinePanel: rename _sidebarView to _recordsView

TimelineView has member _sidebarView which is actually is a top level
container for records.

DriveBy: rearrange groups of calls that relate to recordsView into single
chunk of code.

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/136363003

git-svn-id: svn://svn.chromium.org/blink/trunk@164963 bbb929c8-8fbe-4397-9dbb-9b2b20218538