I get raw MIME data (?) even if in step 1 I put an image on the clipboard. Seems more like a problem with the Copy Image command when working with the images.google.com page (I can't reproduce on other web pages). This is on the Mac.

I can repro it with Bing images (bing.com/images) as well.
I can copy same image (from bing) using edge and paste it on webpage on Chrome or paint.

Able to reproduce this issue on Mac OS 10.12 using chrome latest stable M55-55.0.2883.87 by following steps mentioned in the original comment. Observed the image is not getting pasted in gmail.

Bisect information only for Mac:
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Good build: 51.0.2696.0
Bad Build : 51.0.2698.0

You are probably looking for a change made after 384732 (known good), but no later than 384762 (first known bad).

Change Log URL: https://chromium.googlesource.com/chromium/src/+log/bd4c6ac99e771e0d5893b25d8058d3153efb6fa1..d4e8c65ad84d47cbd436d05d7ec5393bd68194f9

Unable to find the actual suspect from the above log, could anyone please help us in assigning this issue to the right owner.

Note:
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Tested the same on Windows-10 High Dpi by following the similar steps and observed different behavior. By pasting the image in gmail different image is getting pasted from the same page. There was a similar  issue 667223  which got fixed recently. No issues observed by testing the same on Ubuntu 14.04, observed copy pasting image works fine as expected.

Doesn't reproduce on canary. I'm assuming it's the same as  issue 667223 .

hy in vers. chrome beta 63.0.3239.59 (Build ufficiale) beta (a 64 bit) still present problem for select text body mail and also the body in replay goes to attach! do u think u 'll solve this big problem?

Still present on Chrome OS Version 67.0.3396.99 (Official Build) (64-bit)

If the image is loaded directly (ie right click, open image in new tab) Chrome copies the image to the clipboard as intended.