[CSS Shapes] Add basic support for shape-inside with inline/block content with floats
    
Float positioning inside shape-inside has been working only for simple cases when the float boundaries didn't overlap with the shape.
This patch introduces the basic support for left floats and shapes with inline content, and shapes with block content with inline content (paragraphs).
This patch doesn't add test cases for float content with border/margin/padding, for those cases I'll make a separate patch.
    
Merged WebKit Revisions:
- http://trac.webkit.org/changeset/156846
- http://trac.webkit.org/changeset/156107
- http://trac.webkit.org/changeset/156022

Review URL: https://codereview.chromium.org/26926002

git-svn-id: svn://svn.chromium.org/blink/trunk@159472 bbb929c8-8fbe-4397-9dbb-9b2b20218538