Removing dead code related to webkit-prifixed canvas2d line dash feature

This API never shipped in Chrome (bindings were only implemented for JSC and
not V8) so this code has been dead since the blink fork.

BUG=341566
R=senorblanco@chromium.org

Review URL: https://codereview.chromium.org/143573007

git-svn-id: svn://svn.chromium.org/blink/trunk@166656 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add image loading spec related tests

Added the following layout tests:
* Setting order of crossOrigin and src attributes in JS doesn't change outgoing request
* Setting order of srcset and src attributes in JS doesn't change fetched resources
* Setting innerHTML with an <img> inside triggers a resource load
* Setting src of a cached image exposes its width immediately

BUG=

Review URL: https://codereview.chromium.org/136693020

git-svn-id: svn://svn.chromium.org/blink/trunk@166657 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use a RefPtr<HistoryItem> in HistoryFrameLoadSet.

BUG=341220
TEST=http/tests/navigatin/same-and-different-back.html

Review URL: https://codereview.chromium.org/156923002

git-svn-id: svn://svn.chromium.org/blink/trunk@166658 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Mark inspector/tracing.html as failing.

Unreviewed gardening.

BUG=341641
TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/138703007

git-svn-id: svn://svn.chromium.org/blink/trunk@166659 bbb929c8-8fbe-4397-9dbb-9b2b20218538