Improved srcset descriptor parsing.
I've refactored srcset's descriptor parser in order to improve readability of the srcset parser, and improve spec compliance.
Changes:
* Descriptor parsing is now split to its own function.
* Invalid descriptors are ignored, rather than invalidate the candidate.
- That includes the viewport qualifiers, which are not yet supported, but may be used by authors.
* Some unnecessary cruft has been removed from the srcset parser.
* Added tests that make sure descriptors are treated as they should.
BUG=
Review URL: https://chromiumcodereview.appspot.com/23694049
git-svn-id: svn://svn.chromium.org/blink/trunk@158167 bbb929c8-8fbe-4397-9dbb-9b2b20218538
7 files changed
