Chrome Version: 57.0.2970.0 (Official Build) dev (64-bit)
OS: ChromeOS

What steps will reproduce the problem?
(1) Find a page or extension with a large heap (in my case an extension w/ a 375MB JS heap)
(2) Open Developer Tools and choose Memory.
(3) Take a heap snapshot.

What is the expected result?

(1) Expect that taking a snapshot increases memory usage, but no more than, say, 2x.
(2) Expect that the snapshot is, or at least can be, saved to persistent storage before being visualized.

What happens instead?

(1) Taking a heap snapshot caused the extension renderer process to balloon to ~1.6GB in size (i.e. an increase of about 4-5x), placing it close to the 2GB renderer memory limit. To try to debug the high memory condition almost OOM'd the renderer :P

(2) Once the snapshot was captured, Developer Tools decided to load it. This consumed ~1.2GB at peak (3-4x the extension's original memory footprint). This was in addition to the extension itself still holding 1.6GB of RAM, so an overall overhead of about 7x the memory footprint of the extension.

(3) Even after the snapshot had completed loading, and the extension's memory usage dropped down again, it stayed at around 750MB (about double the original usage) until Developer Tools was stopped.