Fix getBBox() returning (0,0) bug when width or height is zero
    
For rects/ellipses with width or height of 0, getBBox() returns the
bounding box as being empty. This patch fixes this bug.
    
It ports and extends one initial patch, fixing the isEmpty() check,
by Changhun Kang <temoochin@company100.net>
    
On top of Changhun's patch, this patch addresses the case where
rects/ellipses fall back to renderSVGShape and their fill bounding box
should not fall back.
    
In detail, this patch involves the following:
    
- Patch for the bug (RenderSVGEllipse, RenderSVGRect and SVGPathData)
- Three new test cases for rect, ellipse and circle
- Current layout tests updated under platform/linux
- Updated TestExpectations

BUG=140472

Review URL: https://codereview.chromium.org/208323007

git-svn-id: svn://svn.chromium.org/blink/trunk@170097 bbb929c8-8fbe-4397-9dbb-9b2b20218538