Move the common parsing logic for intrinsicSize attribute to a shared namespace

The logic for parsing intrinsicSize attribute is shared among
HTML{Image,Video}Element and SVGImageElement. Moving it to
blink/core/html/media/media_element_parser_helpers to avoidredundant
code.

Bug: 874629
Change-Id: I20e1dc6b626eb86e8919c621b1c98401eaa9d201
Reviewed-on: https://chromium-review.googlesource.com/1217163
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Luna Lu <loonybear@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590008}
7 files changed