Use base::Clock instead of base::Time::Now in AppSearchProvider.

chrome/browser/ui/app_list/search/app_result.cc

 // Copyright 2013 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 "chrome/browser/ui/app_list/search/app_result.h"
 
 #include "base/time/time.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_util.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 63 matching lines @@
     tags.push_back(Tag(Tag::MATCH, hits[i].start(), hits[i].end()));
 
   set_title(title.text());
   set_title_tags(tags);
   set_relevance(match.relevance());
 }
 
 void AppResult::UpdateFromLastLaunched(const base::Time& current_time,
                                        const base::Time& last_launched) {
   base::TimeDelta delta = current_time - last_launched;
-  DCHECK_LE(0, delta.InSeconds());
+  if (current_time < last_launched) {

[Matt Giuca, 2014/12/10 07:16:12]

This certainly needs an explanation. (From the bug, I understand that this is a
"basically can never happen except on full moon" scenario, so you should vaguely
explain it and say why you do 1.0.)

[calamity, 2014/12/11 05:05:01]

Done.

+    set_relevance(1.0);
+    return;
+  }
+
   const int kSecondsInWeek = 60 * 60 * 24 * 7;
 
   // Set the relevance to a value between 0 and 1. This function decays as the
   // time delta increases and reaches a value of 0.5 at 1 week.
   set_relevance(1 / (1 + delta.InSecondsF() / kSecondsInWeek));
 }
 
 void AppResult::Open(int event_flags) {
   RecordHistogram(APP_SEARCH_RESULT);
   const extensions::Extension* extension =
@@ skipping 105 matching lines @@
                                   const extensions::Extension* extension) {
   UpdateIcon();
 }
 
 void AppResult::OnShutdown(extensions::ExtensionRegistry* registry) {
   DCHECK_EQ(extension_registry_, registry);
   StopObservingExtensionRegistry();
 }
 
 }  // namespace app_list