sync: Fix serialization in proto_value_conversions
sync: Fix serialization in proto_value_conversions

Adds proper serialiation for the 'initial_sync_in_progress' flag.

This should have been part of r284159.

BUG=351005

Review URL: https://codereview.chromium.org/453143002

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@288494 0039d316-1c4b-4281-b951-d872f2087c98

bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,littlstar/chromium.src,bright-sparks/chromium-spacewalk,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,littlstar/chromium.src,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,ondra-novak/chromium.src