Update existing uses of /wd4267 to use the GN config

This is the size_t to integer conversion warning. Using the config prevents flag duplication and is clearer to read.

Minor updates to Win64 build, including some fixes for size_t to int conversions.

Review URL: https://codereview.chromium.org/929793006

Cr-Commit-Position: refs/heads/master@{#317162}
64 files changed