This review merges the two existing page serializers, WebPageSerializerImpl and
PageSerializer, into one, PageSerializer. In addition to this it moves all
the old tests from WebPageNewSerializerTest and WebPageSerializerTest to the
PageSerializerTest structure and splits out one test for MHTML into a new
MHTMLTest file.

Saving as 'Webpage, Complete', 'Webpage, HTML Only' and as MHTML when the
'Save Page as MHTML' flag is enabled now uses the same code, and should thus
have the same feature set. Meaning that both modes now should be a bit better.

Detailed list of changes:

- PageSerializerTest: Prepare for more DTD test
- PageSerializerTest: Remove now unneccesary input image test
- PageSerializerTest: Remove unused WebPageSerializer/Impl code
- PageSerializerTest: Move data URI morph test
- PageSerializerTest: Move data URI test
- PageSerializerTest: Move namespace test
- PageSerializerTest: Move SVG Image test
- MHTMLTest: Move MHTML specific test to own test file
- PageSerializerTest: Delete duplicate XML header test
- PageSerializerTest: Move blank frame test
- PageSerializerTest: Move CSS test
- PageSerializerTest: Add frameset/frame test
- PageSerializerTest: Move old iframe test
- PageSerializerTest: Move old elements test
- Use PageSerizer for saving web pages
- PageSerializerTest: Test for rewriting links
- PageSerializer: Add rewrite link accumulator
- PageSerializer: Serialize images in iframes/frames src
- PageSerializer: XHTML fix for meta tags
- PageSerializer: Add presentation CSS
- PageSerializer: Rename out parameter

BUG=
R=abarth@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=162155

Review URL: https://codereview.chromium.org/68613003

git-svn-id: svn://svn.chromium.org/blink/trunk@162294 bbb929c8-8fbe-4397-9dbb-9b2b20218538