Recently, I've found that when using the pinch-to-zoom motion with the trackpad while reading a PDF in Chrome, I no longer get the preferred behavior: Chrome's zoom ticking up discretely by 25% or so. Instead, I get a continuous "screen-zoom" effect (similar to holding Control and scrolling), inside the Chrome window (as opposed to the actual screen-zoom, which is independent of the application). Chrome's usual zoom controls still work, but I have to access them either by keyboard shortcut or clicking the respective buttons.
There are several down-sides: the resolution does not update, so my zoomed-in PDF is unnecessarily grainy, and I cannot use horizontal scrolling to navigate, only vertical. Further, the zoom happens wherever the cursor is, rather than centered in the page. Finally, there is a fixed upper bound to how far I can zoom in. This is all rather strange and unwieldily; how can I recover the original behavior?
I am using OSX 10.9.5, and the most recent version of Chrome. All four "Scroll and Zoom" options under Trackpad in System Preferences are active. If I deactivate 'Pinch to zoom', instead of recovering the old behavior, nothing happens when I pinch.
Thanks for your help!