The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/886546446df947816927a7757de45fab1646c919

commit 886546446df947816927a7757de45fab1646c919
Author: fs <fs@opera.com>
Date: Wed Apr 27 09:13:10 2016

Don't use a magic value for 'auto' oriented <marker>s

The value -1 (degrees) is a valid angle, so using it to indicate that
'auto' orientation should be used does not work out.
Just check 'orientType' directly instead and simplify the angle getter.

BUG= 606345 

Review URL: https://codereview.chromium.org/1916173003

Cr-Commit-Position: refs/heads/master@{#390029}

[add] https://crrev.com/886546446df947816927a7757de45fab1646c919/third_party/WebKit/LayoutTests/svg/markers/marker-orientation-minus-one-expected.html
[add] https://crrev.com/886546446df947816927a7757de45fab1646c919/third_party/WebKit/LayoutTests/svg/markers/marker-orientation-minus-one.html
[modify] https://crrev.com/886546446df947816927a7757de45fab1646c919/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceMarker.cpp
[modify] https://crrev.com/886546446df947816927a7757de45fab1646c919/third_party/WebKit/Source/core/layout/svg/SVGLayoutTreeAsText.cpp