VS 2015 has a new or louder warning about 32-bit shifts that are then
assigned to a 64-bit target. This type of code triggers it:
int64_t size = 1 << shift_amount;
Because the '1' being shifted is a 32-bit int the result of the shift
will be a 32-bit result, so assigning it to a 64-bit variable is just
misleading.
In this case the code that triggers it is this:
size_t window_size = static_cast<size_t>(1 << shift_amount);
The destination is a size_t so the warning only shows up on 64-bit
builds and doesn't indicate a real bug. It's curious that the code
had a cast already - presumably to suppress some other warning - but
the cast is not in the ideal place and doesn't avoid this new warning.
Moving the cast allows shift_amount to be log2(size_t) and allows
enabling C4334 in Chromium.
BUG=593448
Review URL: https://codereview.webrtc.org/1849753004
Cr-Commit-Position: refs/heads/master@{#12199}
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