text-size-adjust adjusts font sizes on mobile devices. Values other than auto disable automatic text size adjustments. Percentage values increase the computed size of text. This makes text-size-adjust more consistent, so it works like a direct multiplier of the font size (and line height). The major changes are: * text-size-adjust works with or without a meta viewport. * non-auto values disable ALL automatic text size adjustments. * percentages apply directly, without any heuristics. * layout bugs are fixed.
Explainer with more information about the exact changes: https://docs.google.com/document/d/1l3LFl_kDDoScUlXTcBXsnj2RbeU9zXo1DqNfctY84p0/edit?usp=sharing