Improve symbol_extractor.CreateNameToSymbolInfo handling of duplicate symbols.
If a symbol appears more than once in the binary, return the lowest offset for
that symbol, rather than the last one. Also warn about duplicated symbols.
There are a couple hundred in libchrome.so. Further investigation is needed to
determine why this is even possible, but in the mean time this should fix the
orderfile bot redness.
Review URL: https://codereview.chromium.org/
947073003
Cr-Commit-Position: refs/heads/master@{#317592}