Separate webplatform profile data into a shared, common directory. Use IPC mechanism to enable safe multi-process access to these data files. Webplatform profile data includes: cert8.db key3.db secmod.db cookies.txt prefs.js Cache/* This list may also include hostperm.1 at some point. Possible file structure (linux perspective): Shared profile data: ~/.mozilla/toolkit/default.abc/ Firefox profile data: ~/.mozilla/firefox/default.efg/ Tbird profile data: ~/.mozilla/thunderbird/default.hij/ Embedders of the XUL toolkit (via the xulrunner or straight XRE embedding) should be able to define their application name, and have profile data live under ~/.mozilla/{$app-name}/default.xyz/ and have access to the shared profile data under ~/.mozilla/toolkit/default.abc/. We may also want to support a mode in which embedders do not have to run with an application specific profile directory. A core feature of pref sharing is the ability for applications to define the subset of preferences that are shared (or inherited from the shared profile location).

bug 250856 / bug 135061 seems to be about the cache part of this

Adding dependency on bug 408156, which addresses the issue of defining different sets of preferences and splitting the preferences file accordingly.