/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/ is in libclosure-compiler-java-doc 20130227+dfsg1-8.
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/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.LineMapping.Builder.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.LineMapping.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.LineMappingOrBuilder.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.OriginalMapping.Builder.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.OriginalMapping.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.OriginalMappingOrBuilder.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/Mapping.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/package-frame.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/package-summary.html
/usr/share/doc/libclosure-compiler-java/api/com/google/debugging/sourcemap/proto/package-tree.html