There is a new commit that points to Chromebooks having the ability to pinch-to-zoom on the touchpad is coming. Right now, in Chrome OS, the ability to zoom in and out on your touchpad is disabled on the vast majority of devices. Only high end models like the Samsung Chromebook Pro and Plus, as well as the Google Pixelbook, have it enabled by default.
That is likely to change. This new commit suggests that it will be enabled by default on any new Chromebooks but will also retroactively be enabled on existing devices.
Chrome OS in general supports a lot of gestures with the touchpad but for whatever reason, the pinch-to-zoom feature was disabled by default. In this commit, it appears that all this will boil down to is setting a flag to enable it by default.
On your current Chromebook, you can go to chrome://flags and do a search for “pinch”. If you have it (not all builds do), you can enable it, restart your browser and it should work. If you don’t find the flag, don’t fret to much over it. You’ve lived without it this long, right?
When exactly this will be enabled on everyone’s devices by default isn’t clear but it is likely going to be soon, perhaps Chrome 65 next month.
Source: XDA Developers