What steps will reproduce the problem?
(1) Run a Polychrome browser with --enable-features=ViewsBrowserWindows and DCHECK enabled
(2) Focus the Omnibox
(3) Command + Control + Spacebar

What is the expected result?
Character viewer appears

What happens instead?
DCHECK in Crashpad and crash

Root cause:
In [BrowserCrApplication sendEvent:], we log the event description to a crash key. However, this particular event returns a string of length 1 and contents NUL for event.characters, which gets baked into the event's description. Since the description contains an embedded NUL, Crashpad DCHECKs.