Version: 51.0.2698.0 canary (64-bit)
OS: Mac OSX 10.11.4

What steps will reproduce the problem?
(1) Highlight and copy some text in Chrome, e.g. "Test"
(2) Highlight and copy some other text in Chrome, e.g. "Foo"
(3) Paste (Ctrl+P) the text somewhere, either in Chrome or another app. Notice the text copied in (1) and (2) are both pasted.

What is the expected output?
"Foo"

What do you see instead?
"Test Foo"

This is not an issue if I copy the text from another app, e.g. a text editor or another browser. I do not see this on stable.