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libpng calculates "filter heuristics" to choose which png
filter to apply.  Chrome need not calculate these "filter
heuristics" because we always choose to use the SUB filter,
for speed.

libpng 1.6 refactors the SUB filter to share code, also
forcing us to calculate the filter heuristics, even though
we don't need to.  This caused a performance regression.

This CL cherry picks a fix from upstream that:
(1) Passes PNG_SIZE_MAX to the filter code.  This allows
the compiler to optimize out the heuristic calculation
code, fixing the performance regression.
(2) Fixes overflow handling in the calculation of filter
heuristics.  This won't affect Chrome.

BUG=619850
BUG=599917

Review-Url: https://codereview.chromium.org/2062423002
Cr-Commit-Position: refs/heads/master@{#401298}