For reference, this is exactly how WebKit is looking for the line: https://code.google.com/searchframe#OAMlx_jo-ck/src/third_party/WebKit/Source/WebCore/inspector/ContentSearchUtils.cpp&exact_package=chromium&q=sourceMappingURL&type=cs&l=143

So this is being a little bit more strict than WebKit, but I say we go with this for now because that's how the sourcemap generators are doing it.