Memory metrics in web applications

In working to find holes in our performance testing in Firefox OS, I
currently see a lack of functionality around the memory space. I'd like to
bring up a couple use cases and see where things go from there.

1. Trigger moment to capture memory information.

Firefox OS uses a custom command-line tool on-device to capture memory
information about a particular web application. We trigger this tool upon
receiving a certain User Timing marker. It would be great if there was a
specific API for capturing the memory at a specific moment in time.

performance.memory.mark()?

2. Fetch peak memory usage

Another useful API for us would be to know metrics about what the peak
memory usage was for a particular web application up until the method call.

performance.memory.peak()?

3. Receive better memory information

In our command-line tool we capture USS, PSS, and RSS of a web application.
I see that Chrome has a proprietary performance.memory API that captures
JS-specific memory information, but expanding this to capture other memory
details would be useful if it is supported on the platform.

Thoughts?

Thanks!

Eli Perelman
Mozilla