Lifetime annotations

Overview

As part of the WebView Multi-profile project, classes and state in `//android_webview/`` will be annotated to make their lifetimes explicit. There are broadly 4 different lifetimes that a class can have:

• Singleton - there is one instance of this class per WebView process. As WebView is run in the embedding app's process, this means there is one instance per embedding app.
• Scoped to Profile - this class is specific to a Profile. It is likely to do with the user's browsing state, such as cookies or permissions.
• Scoped to WebView - this class is specific to a WebView (the Android View), for example the AwZoomControls.
• Temporary - this class has a shorter lifetime than a WebView, likely just existing within a call stack, for example return types.

There is a many to one relationship between WebViews and Profiles. A single Profile can support multiple WebViews, each WebView will only have a single (constant) Profile.

These annotations are purely for documentation, there is no static analysis to check them.

Annotations

In Java, use the following annotations:

• @Lifetime.Singleton
• @Lifetime.Profile
• @Lifetime.WebView
• @Lifetime.Temporary

In C++, use the following comment format as the last line of the classes documentation:

 * Lifetime: Singleton
 * Lifetime: Profile
 * Lifetime: WebView
 * Lifetime: Temporary