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If a symbol was found in multiple object files, we would previously have
changed its object path to be the common ancestor of all paths it
appeared in. This is a problem because it would cause queries based on
path to not find these symbols.

On the flip side, we were creating string literal aliases for every
path a string literal appeared in. For small strings such as "", or
"\n", this would lead to an unreasonable number of aliases.

This changes supersize to first create symbols for all paths, and then
collapse groups with a large number of aliases into a single symbol with
ancestor paths.

Before this change:
.text: 48998 symbols have shared ownership (1553806 bytes)
.rodata: 541 symbols have shared ownership (285728 bytes)

After:
.text: 1586 symbols have shared ownership (48252 bytes)
.rodata: 141 symbols have shared ownership (2828 bytes)

This increases the symbol count 702115->912322 and the file size
9.67mb->10.39mb.

This increases the runtime on my machine from ~40s -> ~42s.

Bug: 776032
Change-Id: I457361762b1f241f114b52464812e6035e881538
Reviewed-on: https://chromium-review.googlesource.com/726460
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510205}