Firefox on Android used to use Electrolysis until it switched to the current Java front-end. And FirefoxOS is using it for sure: process per app, so that apps can be easily killed in low-memory conditions.
As for "legacy add-ons", that would be "every single add-on". Not to mention that the desktop Firefox UI itself would have to be heavily rewritten as well. The judgement, as mcpherinm says, was that the cost was too high for the possible gains. I agree that process isolation is good for security, but there are various other security mitigation strategies that can be used that had a higher bang for the buck at the time.
Firefox on Android used to use Electrolysis until it switched to the current Java front-end. And FirefoxOS is using it for sure: process per app, so that apps can be easily killed in low-memory conditions.
As for "legacy add-ons", that would be "every single add-on". Not to mention that the desktop Firefox UI itself would have to be heavily rewritten as well. The judgement, as mcpherinm says, was that the cost was too high for the possible gains. I agree that process isolation is good for security, but there are various other security mitigation strategies that can be used that had a higher bang for the buck at the time.