It is all explained (but not in a convincing fashion) in
https://bugs.chromium.org/p/chromium/issues/detail?id=451733#c19
https://bugs.chromium.org/p/chromium/issues/detail?id=451733#c66
as a result of:
https://bugs.chromium.org/p/chromium/issues/detail?id=426573
TL;DR : At the time that decision was made, Vista user base was very thin, compared to either the XP or Win7+ one, so for code refactoring/simplification they decided to merge the Vista codepath to the XP one; for Google, it is only numbers that count ; plus, that gave them a perfect opportunity to dump Vista altogether (along with XP) a whole one year prior to Vista SP2 becoming EOL by M$ (and close to 5 years before Vista's Server counterpart, Windows Server 2008 SP2, reaches EOL in Jan 2020 ). Once Google made the first move (dragging along with them all webkit-based browsers), many other software makers soon followed (they had a "nice" justification) in a trend that put Vista, 1.5 years after its official EOL, in the sorry state it is currently in...
The only way to properly fix this is to first grab the source for Chromium 41 (-50?) - Chromium, yes, because Google Chrome itself is closed-source - and then revert
https://chromium.googlesource.com/chromium/src.git/+/f29562d138f8c2222c6f24bddbd1a665ed036658
Some additional details in
https://bugs.chromium.org/p/chromium/issues/detail?id=426573#c10 =>
https://codereview.chromium.org/755293003/diff/1/ui/base/win/shell.cc#newcode153
This isn't a task for the faint-hearted ... You would need a Win7+, 64-bit, machine with lots of RAM and a powerful multi-core CPU, MS Visual Studio 2013+, lots of time/patience and, of course, you should be well versed in that field (compiling open-source browsers in VS)... Two MSFN members come to mind, @roytam1 and @FranceBB, but I am unsure whether they're interested in compiling Google Chrome 49.0.2623.112 (last officially supported build on Vista) or 50.0.2661.102 (last Vista compatible, but not officially supported) with Aero-Glass enabled in Vista... I, as much as other Vista users, would be all up for this, even if it is realised purely as a challenge only, given that both Chrome 49+50 are quite outdated (in both security and performance aspects) when dealing with the web of 2019...
Those two screenshots @VistaPAE posted in OP are not from his own system ...
First one is taken from
https://bugs.chromium.org/p/chromium/issues/detail?id=451733#c83
That person compiled Chromium 49.0.2579.0 64-bit with the aero-disabling commits reverted...
So did this one (Chromium 45.0.2415.0 64-bit) :
https://bugs.chromium.org/p/chromium/issues/detail?id=451733#c68
The second screenshot in the OP is taken from
https://bugs.chromium.org/p/chromium/issues/detail?id=451733#c67
It emerged that this was actually a hoax/cheat ; the OS used to generate the shot is Win7 SP1 64-bit, disguised as Windows Vista (much like @WinClient5270 's guide found in his signature...)
So now you know
PS: For the history of it, the last build on Vista SP2 with Aero turned ON was Google Chrome 41.0.2243.0 in the dev channel; I keep a portable copy of it on my system just for fun, it's not used for normal browsing:
Next build 41.0.2245.0 had Aero turned OFF in Vista...