This adds some dependencies and marks them all public. Since chrome/common doesn't have much of an API or structure, deciding what should be public or not is basically impossible.

Removes the include of content_switches from chrome_switches. Files depending on this have already been updated to include content_switches directly.

Moves the nss_security_manager code out of chrome_browser. This was used only by chrome_common. In GYP This is now part of chrome_common_net. In GN, this is a separate target that chrome_common_net depends on.

Reland of https://codereview.chromium.org/1393953003/
TBR=dpranke

Review URL: https://codereview.chromium.org/1406053002

Cr-Commit-Position: refs/heads/master@{#354391}