[PriceInsights] Fix graph UI with no price changes

If there are no price changes, the line should be in middle of the
history graph, rather than at the bottom. Updated the lower and
upper bound to make the curved line in the middle

This CL also tries to fix that opening the bookmarks side panel leads
to a wrong current url. Suspect the browser is incorrect.

Bug: 1475091
Change-Id: I2fce0052aea9e77fc96dad9308b322b66b6fa679
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4809122


Commit-Queue: Zhiyuan Cai <zhiyuancai@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1187931}