Make `SourceMapManager.Events` available to web tests.
Make `SourceMapManager.Events` available to web tests.

Bug: chromium:1228674
Change-Id: I454b66bc0ece1b397bff7cca39e7d66d70536c22
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3113765
Auto-Submit: Benedikt Meurer <024a1e0af501338d11c3b837c6193d11c140d792@chromium.org>
Reviewed-by: Kateryna Prokopenko <04b7d4bdbd93555cee90f085bb91b72524d21fca@google.com>
Commit-Queue: Benedikt Meurer <024a1e0af501338d11c3b837c6193d11c140d792@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend