Move syncer::kModelTypeInfoMap array to read-only data segment

Due to a quirk in VC++ it is easy to accidentally prevent a const global
array from being placed in the read-only data segment. This change
removes some should-be-harmless 'const' keywords to work around this
quirk and move ~960 bytes to the .rdata (read-only) data segment in
chrome.dll.

VC++ bug is filed here:
https://connect.microsoft.com/VisualStudio/feedback/details/3117602

Other instances of this quirk are also being worked around.

BUG=677351

Review-Url: https://codereview.chromium.org/2605393002
Cr-Commit-Position: refs/heads/master@{#441250}
1 file changed