De Modelos de processos do cromo (ênfase meu):
By default, Chromium creates a renderer process for each instance of a site the user visits. This ensures that pages from different sites are rendered independently, and that separate visits to the same site are also isolated from each other. Thus, failures (e.g., renderer crashes) or heavy resource usage in one instance of a site will not affect the rest of the browser. This model is based on both the origin of the content and relationships between tabs that might script each other. As a result, two tabs may display pages that are rendered in the same process, while navigating to a cross-site page in a given tab may switch the tab's rendering process.
A "site instance" is a collection of connected pages from the same site. We consider two pages as connected if they can obtain references to each other in script code (e.g., if one page opened the other in a new window using Javascript)