Improve WebKitMediaSource exception messages.

BUG=270033

Review URL: https://codereview.chromium.org/163963004

git-svn-id: svn://svn.chromium.org/blink/trunk@167405 bbb929c8-8fbe-4397-9dbb-9b2b20218538
TimelinePanel: do not collapse record when user changes panel.

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/166273012

git-svn-id: svn://svn.chromium.org/blink/trunk@167406 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[SVG] SVGAnimated{Angle,Enumeration} migration to new SVG property impl.

This CL replaces SVGAnimated{Angle,Enumeration} with NewSVGProperty based implementation.

For details, see design doc: https://docs.google.com/document/d/1bg7CUyUszqdwmENY3JX6_PoQD6uHRCNcRPJMlC4qlkw/edit?usp=sharing

Specifically: https://docs.google.com/a/chromium.org/document/d/1bg7CUyUszqdwmENY3JX6_PoQD6uHRCNcRPJMlC4qlkw/edit#heading=h.334mf2y4evy5
BUG=308818
NOTRY=true

Review URL: https://codereview.chromium.org/165893003

git-svn-id: svn://svn.chromium.org/blink/trunk@167407 bbb929c8-8fbe-4397-9dbb-9b2b20218538