The Pixel 3 and Pixel 3 XL are rumored to be coming with Active Edge, the feature that was found on the Pixel 2 and Pixel 2 XL from 2017 which allowed the user to squeeze the sides of the phone to interact with sensors that were embedded there, which in turn would transform that recognized pressure into an action for the device, whether it be launching an app or perhaps just silencing the phone.
According to the rumor, details have been found in the code that mention both Crosshatch and Blueline in reference to the Active Edge feature. Crosshatch is said to be the Pixel 3 XL based on earlier leaked information, and so it's suspected that Blueline is in reference to the Pixel 3. These details suggest that Google is planning to bring the Active Edge feature back for its upcoming phones which are expected to be released a little bit later this year, and although there is always a possibility this may not be the case, it was well-received on the Pixel 2 and Pixel 2 XL so there would be no reason for Google to remove it from its next-gen phones.
This is so far the only information regarding the squeeze functionality for the Pixel 3 series devices but if it is planned to be an included feature then chances are more information will show up leading up to Google's eventual unveiling of the Pixel 3 and Pixel 3 XL in the future. This could be anything from a splash screen that shows people how to set up and use the feature to additional code found within a later build of the Android P beta, as Google was reported to be releasing four or five preview builds of the software, and only just recently released the third preview build. If the feature does make a return, it's unclear if Google will keep the functionality the same as it is on the Pixel 2 and Pixel 2 XL or if it will expand on it and enable it to do more for the user.