Fix IsPrecachingAllowed() to check Sync instead of Data Saver.

components/precache/content/precache_manager.h

Index: components/precache/content/precache_manager.h
diff --git a/components/precache/content/precache_manager.h b/components/precache/content/precache_manager.h
index b69ad138330c882ae49a34fc37f6ed32a6ae2011..d2e21a85995830ff73bb43c3f6e483cc915de7f4 100644
--- a/components/precache/content/precache_manager.h
+++ b/components/precache/content/precache_manager.h
@@ -32,6 +32,10 @@ namespace history {
 class HistoryService;
 }
 
+namespace sync_driver {
+class SyncService;
+}
+
 namespace precache {
 
 class PrecacheDatabase;
@@ -52,7 +56,8 @@ class PrecacheManager : public KeyedService,
  public:
   typedef base::Closure PrecacheCompletionCallback;
 
-  explicit PrecacheManager(content::BrowserContext* browser_context);
+  explicit PrecacheManager(content::BrowserContext* browser_context,
+                           sync_driver::SyncService* sync_service);
   ~PrecacheManager() override;
 
   // Returns true if precaching is enabled as part of a field trial or by the
@@ -95,6 +100,10 @@ class PrecacheManager : public KeyedService,
   // The browser context that owns this PrecacheManager.
   content::BrowserContext* browser_context_;
 
+  // The sync service corresponding to the browser context. Used to determine
+  // whether precache can run. May be null.
+  sync_driver::SyncService* sync_service_;
+
   // The PrecacheFetcher used to precache resources. Should only be used on the
   // UI thread.
   scoped_ptr<PrecacheFetcher> precache_fetcher_;