DevTools failed to load SourceMap: Could not load content for chrome-extensi code example

Example 1: how to delete alert "DevTools failed to load SourceMap: Could not load content for chrome-extension"

just "disabled"  javaScript source maps at config section

Example 2: DevTools failed to load SourceMap: Could not load content for

Open Developer Tools, 
go to "Settings" for Developer Tools, 
then uncheck Enable JavaScript Sourcemaps under the "Sources" settings.
Restart Browser if needed