Shift by the right number of bytes when grabbing the high 32 bits.
Shift by the right number of bytes when grabbing the high 32 bits.

When size_t is not 64 bits (8 bytes) but instead N < 8 bytes, we
want to grab the top N bytes from the 64-bit result.

This code was meant to do this:
hash64 >> (sizeof(uint64) - sizeof(std::size_t))

But this translates to:
hash64 >> (8 - N)

And 8-N is the number of bytes we want to shift, not the number of
bits, where as operator>> excepts a number of bits.

Fix this to correct the algorithm for platforms with small size_t.

R=ajwong
BUG=

Review URL: https://codereview.chromium.org/156103003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@253557 0039d316-1c4b-4281-b951-d872f2087c98

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