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-Original-Commit-Position: refs/heads/master@{#317162}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d1c719acf7db459016f425eb8018ec4208511578
1 file changed