[translate] Defer start of translate ranker model load to first use.

components/translate/core/browser/translate_ranker_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/translate/core/browser/translate_ranker_impl.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 138 matching lines @@
       is_decision_override_enabled_(base::FeatureList::IsEnabled(
           translate::kTranslateRankerDecisionOverride)),
       weak_ptr_factory_(this) {
   if (is_query_enabled_ || is_enforcement_enabled_ ||
       is_decision_override_enabled_) {
     model_loader_ = base::MakeUnique<RankerModelLoader>(
         base::Bind(&ValidateModel),
         base::Bind(&TranslateRankerImpl::OnModelAvailable,
                    weak_ptr_factory_.GetWeakPtr()),
         model_path, model_url, kUmaPrefix);
-    // Kick off the initial load from cache.
-    model_loader_->NotifyOfRankerActivity();
   }
 }
 
 TranslateRankerImpl::~TranslateRankerImpl() {}
 
 // static
 base::FilePath TranslateRankerImpl::GetModelPath(
     const base::FilePath& data_dir) {
   if (data_dir.empty())
     return base::FilePath();
@@ skipping 203 matching lines @@
   }
 }
 
 }  // namespace translate
 
 std::ostream& operator<<(std::ostream& stream,
                          const translate::TranslateRankerFeatures& features) {
   features.WriteTo(stream);
   return stream;
 }