Remove source line tracking from MediaList and related DevTools code

Now that the DevTools can track the source range related to CSSMedia,
MediaList::m_sourceLine and CSS.CSSMedia.sourceLine are no longer needed.

R=pfeldman, vsevik, yurys@chromium.org
BUG=none

Review URL: https://chromiumcodereview.appspot.com/17112022

git-svn-id: svn://svn.chromium.org/blink/trunk@152716 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-closing at unexpected EOF for all entry points.

Don't wrap non-stylesheet (CSSOM rule, selectors, etc) input strings to CSS
parser in braces as that will break auto-closing of blocks, parentheses, etc
in the actual input string.

BUG=163354

Review URL: https://chromiumcodereview.appspot.com/17129003

git-svn-id: svn://svn.chromium.org/blink/trunk@152717 bbb929c8-8fbe-4397-9dbb-9b2b20218538
CSS Background Blending doesn't work for gradient layers.

The blending operation won't be performed for any of the background layers
located under a gradient background. The fix consisted of adding the blend mode
operator when drawing the gradient in GeneratorGeneratedImage.

Also adding a few tests validating different ways of using background blending
with gradient layers.

BUG=251239

Review URL: https://chromiumcodereview.appspot.com/17389004

git-svn-id: svn://svn.chromium.org/blink/trunk@152718 bbb929c8-8fbe-4397-9dbb-9b2b20218538