Revert 151169 - [sync] Enable sync credential caching by default for post-M22 builds

Revert 151169 - [sync] Enable sync credential caching by default for post-M22 builds

Reason for revert: See bug 143214. CredentialCacheService::GetLastUpdatedTime() is causing a crash in canary builds during upgrade scenarios from older versions. A real fix for the root cause is under review. The earlier revert in https://chromiumcodereview.appspot.com/10830362 is unlikely to fix the root cause. Until then, the safe thing to do is to disable the feature, by reverting r151169.

Original CL description:

Sync credential caching is a Win 8 feature that allows Metro and Desktop
to share sync credentials under some circumstances. The feature is
slated to ship with M23, and was disabled for the M22 branch point.
Now that M22 has been branched off, it is time to re-enable the feature.

This patch turns on the feature by default, and provides users with the
"--disable-sync-credential-caching" flag if the feature must be disabled.

BUG=139712, 143214
TEST=Sign in on Win 8 and make sure that "Sync Credentials" is written to the default profile directory
Old review URL: https://chromiumcodereview.appspot.com/10855063

TBR=tim@chromium.org,zea@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=151976