Properly handle disabling sync via the google dashboard.

chrome/browser/signin/signin_manager.cc

Index: chrome/browser/signin/signin_manager.cc
diff --git a/chrome/browser/signin/signin_manager.cc b/chrome/browser/signin/signin_manager.cc
index a5047b1c67b08008e295a9f976357fa2fe1a686e..fb94eb1c3942f6f45af04b458eb937f439ec71f8 100644
--- a/chrome/browser/signin/signin_manager.cc
+++ b/chrome/browser/signin/signin_manager.cc
@@ -194,6 +194,7 @@ bool SigninManager::IsAllowedUsername(const std::string& username,
 
 SigninManager::SigninManager()
     : profile_(NULL),
+      prohibit_signout_(false),
       had_two_factor_error_(false),
       type_(SIGNIN_TYPE_NONE),
       weak_pointer_factory_(this) {
@@ -542,6 +543,10 @@ void SigninManager::HandleAuthError(const GoogleServiceAuthError& error,
 
 void SigninManager::SignOut() {
   DCHECK(IsInitialized());
+  if (prohibit_signout_) {
+    DVLOG(1) << "Ignoring attempt to sign out while signout is prohibited";
+    return;
+  }
   if (authenticated_username_.empty() && !client_login_.get()) {
     // Clean up our transient data and exit if we aren't signed in (or in the
     // process of signing in). This avoids a perf regression from clearing out
@@ -889,6 +894,14 @@ void SigninManager::Shutdown() {
   }
 }
 
+void SigninManager::ProhibitSignout() {
+  prohibit_signout_ = true;
+}
+
+bool SigninManager::IsSignoutProhibited() const {
+  return prohibit_signout_;
+}
+
 void SigninManager::OnGoogleServicesUsernamePatternChanged() {
   if (!authenticated_username_.empty() &&
       !IsAllowedUsername(authenticated_username_)) {