Chrome suggestions are no longer served if the user doesn't sync his history on a given machine

chrome/browser/ui/search/search_tab_helper.cc

Index: chrome/browser/ui/search/search_tab_helper.cc
diff --git a/chrome/browser/ui/search/search_tab_helper.cc b/chrome/browser/ui/search/search_tab_helper.cc
index b117ad020d24c398cc3042ed0019dc3e3e713317..cd435dff683168d95a4bc61e1ba4cdcd73c02a2b 100644
--- a/chrome/browser/ui/search/search_tab_helper.cc
+++ b/chrome/browser/ui/search/search_tab_helper.cc
@@ -17,6 +17,8 @@
 #include "chrome/browser/search/instant_service_factory.h"
 #include "chrome/browser/search/search.h"
 #include "chrome/browser/signin/signin_manager_factory.h"
+#include "chrome/browser/sync/profile_sync_service.h"
+#include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/browser/ui/app_list/app_list_util.h"
 #include "chrome/browser/ui/browser_navigator.h"
 #include "chrome/browser/ui/browser_window.h"
@@ -120,6 +122,16 @@ void RecordNewTabLoadTime(content::WebContents* contents) {
   core_tab_helper->set_new_tab_start_time(base::TimeTicks());
 }
 
+// Returns true if the user is signed in and full history sync is enabled,
+// and false otherwise.
+bool IsHistorySyncEnabled(Profile* profile) {
+  ProfileSyncService* sync =
+      ProfileSyncServiceFactory::GetInstance()->GetForProfile(profile);
+  return sync &&
+      sync->sync_initialized() &&
+      sync->GetActiveDataTypes().Has(syncer::HISTORY_DELETE_DIRECTIVES);

[Jered, 2014/06/17 22:38:19]

I don't understand what HISTORY_DELETE_DIRECTIVES is or does, but I'll trust
that this is what you need.

[beaudoin, 2014/06/18 13:49:04]

It's the one used by other pieces of the code that look at that checkbox state.
I verified it works. Maybe SESSIONS would work too, but I'd rather go with the
one everybody else is using.

+}
+
 }  // namespace
 
 SearchTabHelper::SearchTabHelper(content::WebContents* web_contents)
@@ -526,8 +538,11 @@ void SearchTabHelper::OnChromeIdentityCheck(const base::string16& identity) {
   if (manager) {
     const base::string16 username =
         base::UTF8ToUTF16(manager->GetAuthenticatedUsername());
-    ipc_router_.SendChromeIdentityCheckResult(identity,
-                                              identity == username);
+    // The identity check only passes if the user is syncing their history.
+    // TODO(beaudoin): Change this function name and related APIs now that it's
+    // checking both the identity and the user's sync state.
+    bool matches = IsHistorySyncEnabled(profile()) && identity == username;
+    ipc_router_.SendChromeIdentityCheckResult(identity, matches);
   }
 }