Eliminate content::BrowserThread knowledge from VariationsService

components/variations/variations_service_client.h

Index: components/variations/variations_service_client.h
diff --git a/components/variations/variations_service_client.h b/components/variations/variations_service_client.h
index 9431630dfe58bada0fb8ac3e41cb88f69755de91..1ac863f95633199f5c3a1ebff85d74a4f14fbfe9 100644
--- a/components/variations/variations_service_client.h
+++ b/components/variations/variations_service_client.h
@@ -7,6 +7,10 @@
 
 #include <string>
 
+namespace base {
+class SequencedWorkerPool;
+}
+
 namespace net {
 class URLRequestContextGetter;
 }
@@ -26,6 +30,10 @@ class VariationsServiceClient {
   // Returns the current application locale (e.g. "en-US").
   virtual std::string GetApplicationLocale() = 0;
 
+  // Returns the SequencedWorkerPool on which the VariationsService should run
+  // tasks that may block.
+  virtual base::SequencedWorkerPool* GetBlockingPool() = 0;
+
   virtual net::URLRequestContextGetter* GetURLRequestContext() = 0;
   virtual network_time::NetworkTimeTracker* GetNetworkTimeTracker() = 0;