Refined h1 warnings checker.
Make URL checker optionally report bad URL value.
Trim URLs to 50 chars in msg from URL checker.
Added ImageCandidateURL.
Use ImageCandidateURL when checking srcset URLs.
Checkpointing srcset datatype checking.
Checkpointing srcset. Ugly but works now (mostly).
Cleanup (no need to valueOf() a CharSequence...).
Streamlined srcset code a bit.
Minor cleanup.
Refine srcset URL trimming & error msg formatting
srcset fixup & streamlining.
Finished adding checks for all srcset requirements.
Fix to handle all missing-width cases.
Catch some more srcset error cases.
Minor cleanup.
Minor cleanup.