Make glic size animations preserve the top left corner position

Previously the size animations kept the top right corner in the same
spot. Now there is just one animation that can change the panel width
and it's meant to keep the top left corner stationary.

Bug: 409788634
Change-Id: I26387d0697fbd2342a226c9665a39f07b934e5d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6448291
Commit-Queue: Ian Wells <iwells@chromium.org>
Reviewed-by: Sana Akbani <sanaakbani@google.com>
Commit-Queue: Sana Akbani <sanaakbani@google.com>
Auto-Submit: Ian Wells <iwells@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1445389}