[CSS Blending] Add test suite to validate Background Layers Blending
CSS Background Blending should be performed, regardless the background layer possible combinations.
Adding tests for the following use cases:

* Bg blend mode for an element with just one image as the background.
* Bg blending for an image and a background color. Different background images should be tested,
having different formats, such as png or jpg.
* Bg blending for an image on top of another image. 
* Bg blending for an image on top of a background color. 
* Blend 3 background images, specify less blend modes in CSS.

BUG=251727

Review URL: https://chromiumcodereview.appspot.com/17465004

git-svn-id: svn://svn.chromium.org/blink/trunk@152791 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Inspector: Fixed exception related to DevToolsSanityTest.TestReattachAfterCrash flakiness

According to the log in the bug an exception happens at a line that is now at Source/devtools/front_end/Drawer.js:111.

Added a speculative null check. 

BUG=163411

Review URL: https://chromiumcodereview.appspot.com/17371004

git-svn-id: svn://svn.chromium.org/blink/trunk@152792 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [CodeMirror] Roll CodeMirror to v3.14

This patch rolls CodeMirror to v3.14

BUG=
R=vsevik@chromium.org

Review URL: https://codereview.chromium.org/17496007

git-svn-id: svn://svn.chromium.org/blink/trunk@152793 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Adding MediaSource LayoutTests that verify seek during a pending seek behavior.

These tests verify that the HTMLMediaElement seeking logic works as expected
when a MediaSource application doesn't append data to satisfy one seek before
the next seek is requested.

BUG=144471

Review URL: https://chromiumcodereview.appspot.com/17101031

git-svn-id: svn://svn.chromium.org/blink/trunk@152794 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: use Element.remove() instead of removeSelf() and parentElement.removeChild()

This switches front-end to using Element.remove() instead of its hand-crafted replacement
in DOMExtensions.js or calls to parentElement.removeChild().

R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/17101022

git-svn-id: svn://svn.chromium.org/blink/trunk@152795 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Support live edit syntax error positions highlighting in front-end

Review URL: https://chromiumcodereview.appspot.com/17494003

git-svn-id: svn://svn.chromium.org/blink/trunk@152796 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Do not consider title from non-css stylesheet for preferred set.

Title on a style element can be used to select the preferred stylesheet set.
If the type attribute of the style element is not text/css, the title should
never be set as the key for the preferred stylesheet set.

BUG=252215

Review URL: https://chromiumcodereview.appspot.com/17496004

git-svn-id: svn://svn.chromium.org/blink/trunk@152797 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [CodeMirror] CodeMirrorTextEditor to support long lines

This patch does couple of things which result in bearable long lines
support:
[1] This CL patches codemirror.js so that it becomes capable of handling
long lines. These changes are not upstreamed yet (refer to
https://github.com/marijnh/CodeMirror/pull/1613 for details) as they are not
mature enough for the general case, but they suit our needs under certain
conditions (see [2])

[2] This CL adds "longLinesMode" to CodeMirrorTextEditor which gets switched
on in case of long lines. This mode:
- switches off selected text foreground (thus leaves text syntax-highlighted).
This is an implication of poor 'CodeMirror.markText' support (caused by [1])
and the fact that selected text foreground gets highlighted by the method.
- switches off bracket matching as it works far too much for long lines.
This change will be reverted as soon as 'matchbrackets' addon will respect
its 'maxHighlightLineLength' setting.

[3] This CL reduces amount of highlighted symbols per line up to 1000. Thus
said, everything that lays after position #1000 will not be highlighted.

BUG=247320
R=vsevik@chromium.org

Review URL: https://codereview.chromium.org/17437005

git-svn-id: svn://svn.chromium.org/blink/trunk@152798 bbb929c8-8fbe-4397-9dbb-9b2b20218538