Get rid of multiple inheritence for SVGViewElement interface

Web IDL no longer supports multiple inheritence. As per the latest
specification SVGViewElement should only inherit from SVGElement.
'implements' statements are used for the rest. This patch refactors
the IDL files to match the latest specification:
http://www.w3.org/TR/SVG2/linking.html#InterfaceSVGViewElement

Note that there is a WebExposed change as SVGZoomAndPan used to be
exposed on the Window and it is not anymore. SVGZoomAndPan merely
supplements SVGViewElement and should not be exposed to JavaScript
according to the latest specification.

BUG=251772

Review URL: https://chromiumcodereview.appspot.com/16959011

git-svn-id: svn://svn.chromium.org/blink/trunk@152827 bbb929c8-8fbe-4397-9dbb-9b2b20218538
14 files changed