Percent-decode fragments before using them for SVG references

We were using the "raw" form of the fragment, meaning that any percent-
encoded fragments would not resolve correctly.

Bug: 779420
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ic091e775589fd59d25ad1878115f2ad2593bc733
Reviewed-on: https://chromium-review.googlesource.com/746885
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#512895}
6 files changed