[SVG] Skip layout viewport change calculation when not needed.

SVGRenderSupport::layoutChildren() determines whether the size of the
nearest viewport has changed upfront, and then uses this information to
force a re-layout of relative-length children.

But the relative-length flag is always propagated up the ancestor chain
(see SVGElement::updateRelativeLengthsInformation), so we can
immediately tell whether there are any relative-length descendants. If
there aren't, we can skip the viewport change crawl and related logic.

R=pdr@chromium.org,schenney@chromium.org,fs@opera.com,ed@opera.com

Review URL: https://codereview.chromium.org/458833002

git-svn-id: svn://svn.chromium.org/blink/trunk@180071 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Record DevTools metadata events on worker threads when starting recoring tracing based Timeline

This events will be used to figure out if given worker thread is started by the page being profiled and if so we will show messages in the worker on the same Timeline.

BUG=401895

Review URL: https://codereview.chromium.org/460363002

git-svn-id: svn://svn.chromium.org/blink/trunk@180072 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Skia improved GPU canvas-createImageBitmap-colorClamping.html.

The Skia GPU and software do not appear to agree in this case.
The GPU is more correct, the tracking bug is investigating software.


git-svn-id: svn://svn.chromium.org/blink/trunk@180073 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Remove autogenerated blackbox patterns upon Unblackbox user action.

Remove autogenerated patterns instead of just disabling them to avoid cluttering.

BUG=267592
R=vsevik

Review URL: https://codereview.chromium.org/458583004

git-svn-id: svn://svn.chromium.org/blink/trunk@180074 bbb929c8-8fbe-4397-9dbb-9b2b20218538