Introduce //components/user_prefs, use to eliminate c/b/prefs dependency in Autofill.

chrome/browser/autofill/autofill_download.cc

Index: chrome/browser/autofill/autofill_download.cc
diff --git a/chrome/browser/autofill/autofill_download.cc b/chrome/browser/autofill/autofill_download.cc
index 94bc8ba0364fed00dccb3f5cc24b9690080377ea..37b87bd33d74df75cb69fef8001f6733dedb25f0 100644
--- a/chrome/browser/autofill/autofill_download.cc
+++ b/chrome/browser/autofill/autofill_download.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/autofill/autofill_xml_parser.h"
 #include "chrome/browser/autofill/form_structure.h"
 #include "chrome/common/pref_names.h"
+#include "components/user_prefs/user_prefs.h"
 #include "content/public/browser/browser_context.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/load_flags.h"
@@ -59,7 +60,7 @@ AutofillDownloadManager::AutofillDownloadManager(BrowserContext* context,
       fetcher_id_for_unittest_(0) {
   DCHECK(observer_);
   PrefService* preferences =
-      PrefServiceFromBrowserContext(browser_context_);
+      components::UserPrefs::GetInstance()->Lookup(browser_context_);
   positive_upload_rate_ =
       preferences->GetDouble(prefs::kAutofillPositiveUploadRate);
   negative_upload_rate_ =
@@ -148,7 +149,7 @@ void AutofillDownloadManager::SetPositiveUploadRate(double rate) {
   positive_upload_rate_ = rate;
   DCHECK_GE(rate, 0.0);
   DCHECK_LE(rate, 1.0);
-  PrefService* preferences = PrefServiceFromBrowserContext(
+  PrefService* preferences = components::UserPrefs::GetInstance()->Lookup(
       browser_context_);
   preferences->SetDouble(prefs::kAutofillPositiveUploadRate, rate);
 }
@@ -159,7 +160,7 @@ void AutofillDownloadManager::SetNegativeUploadRate(double rate) {
   negative_upload_rate_ = rate;
   DCHECK_GE(rate, 0.0);
   DCHECK_LE(rate, 1.0);
-  PrefService* preferences = PrefServiceFromBrowserContext(
+  PrefService* preferences = components::UserPrefs::GetInstance()->Lookup(
       browser_context_);
   preferences->SetDouble(prefs::kAutofillNegativeUploadRate, rate);
 }