Media Galleries API Scanning: Give cached scan results if no user gesture.

BUG=161119

Review URL: https://codereview.chromium.org/141203004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250517 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 74 insertions, 18 deletions

diff --git a/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc b/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
index bc56c96..73ea1c9 100644
--- a/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
+++ b/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
@@ -657,7 +657,7 @@ void MediaGalleriesStartMediaScanFunction::OnPreferencesInit() {
     return;
   }
 
-  media_scan_manager()->StartScan(GetProfile(), GetExtension()->id());
+  media_scan_manager()->StartScan(GetProfile(), GetExtension(), user_gesture());
   SendResponse(true);
 }
 
@@ -678,7 +678,7 @@ bool MediaGalleriesCancelMediaScanFunction::RunImpl() {
 
 void MediaGalleriesCancelMediaScanFunction::OnPreferencesInit() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  media_scan_manager()->CancelScan(GetProfile(), GetExtension()->id());
+  media_scan_manager()->CancelScan(GetProfile(), GetExtension());
   SendResponse(true);
 }
 
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.cc b/chrome/browser/media_galleries/media_galleries_preferences.cc
index 741d0a2..006fee9 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.cc
+++ b/chrome/browser/media_galleries/media_galleries_preferences.cc
@@ -1088,6 +1088,18 @@ const MediaGalleriesPrefInfoMap& MediaGalleriesPreferences::known_galleries()
   return known_galleries_;
 }
 
+base::Time MediaGalleriesPreferences::GetLastScanCompletionTime() const {
+  int64 last_scan_time_internal =
+      profile_->GetPrefs()->GetInt64(prefs::kMediaGalleriesLastScanTime);
+  return base::Time::FromInternalValue(last_scan_time_internal);
+}
+
+void MediaGalleriesPreferences::SetLastScanCompletionTime(
+    const base::Time& time) {
+  profile_->GetPrefs()->SetInt64(prefs::kMediaGalleriesLastScanTime,
+                                 time.ToInternalValue());
+}
+
 void MediaGalleriesPreferences::Shutdown() {
   weak_factory_.InvalidateWeakPtrs();
   profile_ = NULL;
@@ -1109,6 +1121,10 @@ void MediaGalleriesPreferences::RegisterProfilePrefs(
       prefs::kMediaGalleriesUniqueId,
       kInvalidMediaGalleryPrefId + 1,
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
+  registry->RegisterInt64Pref(
+      prefs::kMediaGalleriesLastScanTime,
+      base::Time().ToInternalValue(),
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
 
 bool MediaGalleriesPreferences::SetGalleryPermissionInPrefs(
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.h b/chrome/browser/media_galleries/media_galleries_preferences.h
index 9b3be73..f868aa3 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.h
+++ b/chrome/browser/media_galleries/media_galleries_preferences.h
@@ -248,6 +248,11 @@ class MediaGalleriesPreferences : public BrowserContextKeyedService,
 
   const MediaGalleriesPrefInfoMap& known_galleries() const;
 
+  // These keep track of when we last successfully completed a media scan.
+  // This is used to provide cached results when appropriate.
+  base::Time GetLastScanCompletionTime() const;
+  void SetLastScanCompletionTime(const base::Time& time);
+
   // BrowserContextKeyedService implementation:
   virtual void Shutdown() OVERRIDE;
 
diff --git a/chrome/browser/media_galleries/media_scan_manager.cc b/chrome/browser/media_galleries/media_scan_manager.cc
index 5aebe16..338fe00 100644
--- a/chrome/browser/media_galleries/media_scan_manager.cc
+++ b/chrome/browser/media_galleries/media_scan_manager.cc
@@ -7,6 +7,7 @@
 #include "base/file_util.h"
 #include "base/files/file_enumerator.h"
 #include "base/logging.h"
+#include "base/time/time.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/media_galleries/media_galleries_preferences.h"
@@ -32,6 +33,9 @@ typedef std::set<std::string /*extension id*/> ScanningExtensionIdSet;
 // directories in the parent directory must be scan results.
 const int kContainerDirectoryMinimumPercent = 80;
 
+// How long after a completed media scan can we provide the cached results.
+const int kScanResultsExpiryTimeInHours = 24;
+
 struct LocationInfo {
   LocationInfo()
       : pref_id(kInvalidMediaGalleryPrefId),
@@ -307,19 +311,39 @@ void MediaScanManager::CancelScansForProfile(Profile* profile) {
 }
 
 void MediaScanManager::StartScan(Profile* profile,
-                                 const std::string& extension_id) {
+                                 const extensions::Extension* extension,
+                                 bool user_gesture) {
+  DCHECK(extension);
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   ScanObserverMap::iterator scans_for_profile = observers_.find(profile);
   // We expect that an MediaScanManagerObserver has already been registered.
   DCHECK(scans_for_profile != observers_.end());
-  bool start_scan = !ScanInProgress();
+  bool scan_in_progress = ScanInProgress();
   // Ignore requests for extensions that are already scanning.
   ScanningExtensionIdSet* scanning_extensions;
   scanning_extensions = &scans_for_profile->second.scanning_extensions;
-  if (!start_scan && ContainsKey(*scanning_extensions, extension_id))
+  if (scan_in_progress && ContainsKey(*scanning_extensions, extension->id()))
     return;
 
+  // Provide cached result if there is not already a scan in progress,
+  // there is no user gesture, and the previous results are unexpired.
+  MediaGalleriesPreferences* preferences =
+      MediaGalleriesPreferencesFactory::GetForProfile(profile);
+  base::TimeDelta time_since_last_scan =
+      base::Time::Now() - preferences->GetLastScanCompletionTime();
+  if (!scan_in_progress && !user_gesture && time_since_last_scan <
+          base::TimeDelta::FromHours(kScanResultsExpiryTimeInHours)) {
+    MediaGalleryScanResult file_counts;
+    int gallery_count =
+        CountScanResultsForExtension(preferences, extension, &file_counts);
+    scans_for_profile->second.observer->OnScanStarted(extension->id());
+    scans_for_profile->second.observer->OnScanFinished(extension->id(),
+                                                       gallery_count,
+                                                       file_counts);
+    return;
+  }
+
   // On first scan for the |profile|, register to listen for extension unload.
   if (scanning_extensions->empty()) {
     registrar_.Add(
@@ -328,8 +352,8 @@ void MediaScanManager::StartScan(Profile* profile,
         content::Source<Profile>(profile));
   }
 
-  scanning_extensions->insert(extension_id);
-  scans_for_profile->second.observer->OnScanStarted(extension_id);
+  scanning_extensions->insert(extension->id());
+  scans_for_profile->second.observer->OnScanStarted(extension->id());
 
   if (folder_finder_)
     return;
@@ -346,17 +370,17 @@ void MediaScanManager::StartScan(Profile* profile,
 }
 
 void MediaScanManager::CancelScan(Profile* profile,
-                                  const std::string& extension_id) {
+                                  const extensions::Extension* extension) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   // Erases the logical scan if found, early exit otherwise.
   ScanObserverMap::iterator scans_for_profile = observers_.find(profile);
   if (scans_for_profile == observers_.end() ||
-      !scans_for_profile->second.scanning_extensions.erase(extension_id)) {
+      !scans_for_profile->second.scanning_extensions.erase(extension->id())) {
     return;
   }
 
-  scans_for_profile->second.observer->OnScanCancelled(extension_id);
+  scans_for_profile->second.observer->OnScanCancelled(extension->id());
 
   // No more scanning extensions for |profile|, so stop listening for unloads.
   if (scans_for_profile->second.scanning_extensions.empty()) {
@@ -389,7 +413,7 @@ void MediaScanManager::Observe(
           content::Details<extensions::UnloadedExtensionInfo>(
               details)->extension);
       DCHECK(extension);
-      CancelScan(profile, extension->id());
+      CancelScan(profile, extension);
       break;
     }
     default:
@@ -437,11 +461,11 @@ void MediaScanManager::OnFoundContainerDirectories(
        ++scans_for_profile) {
     if (scans_for_profile->second.scanning_extensions.empty())
       continue;
+    Profile* profile = scans_for_profile->first;
     MediaGalleriesPreferences* preferences =
-        MediaGalleriesPreferencesFactory::GetForProfile(
-            scans_for_profile->first);
-    ExtensionService* extension_service = extensions::ExtensionSystem::Get(
-        scans_for_profile->first)->extension_service();;
+        MediaGalleriesPreferencesFactory::GetForProfile(profile);
+    ExtensionService* extension_service =
+        extensions::ExtensionSystem::Get(profile)->extension_service();
     if (!extension_service)
       continue;
 
@@ -465,6 +489,7 @@ void MediaScanManager::OnFoundContainerDirectories(
       }
     }
     scanning_extensions->clear();
+    preferences->SetLastScanCompletionTime(base::Time::Now());
   }
   registrar_.RemoveAll();
   folder_finder_.reset();
diff --git a/chrome/browser/media_galleries/media_scan_manager.h b/chrome/browser/media_galleries/media_scan_manager.h
index 8a60403..a04e7ea 100644
--- a/chrome/browser/media_galleries/media_scan_manager.h
+++ b/chrome/browser/media_galleries/media_scan_manager.h
@@ -21,6 +21,10 @@
 class Profile;
 class MediaScanManagerObserver;
 
+namespace extensions {
+class Extension;
+}  // namespace extensions
+
 // The MediaScanManager is owned by MediaFileSystemRegistry, which is global.
 // This class manages multiple 'virtual' media scans, up to one per extension
 // per profile, and also manages the one physical scan backing them.
@@ -41,8 +45,9 @@ class MediaScanManager : public content::NotificationObserver {
   // The results of the scan are reported to the registered
   // MediaScanManagerObserver via OnScanFinished. There must be an observer
   // registered for |profile| before the scan starts.
-  void StartScan(Profile* profile, const std::string& extension_id);
-  void CancelScan(Profile* profile, const std::string& extension_id);
+  void StartScan(Profile* profile, const extensions::Extension* extension,
+                 bool user_gesture);
+  void CancelScan(Profile* profile, const extensions::Extension* extension);
 
  protected:
   friend class MediaGalleriesPlatformAppBrowserTest;
diff --git a/chrome/browser/media_galleries/media_scan_manager_unittest.cc b/chrome/browser/media_galleries/media_scan_manager_unittest.cc
index a64b265..6d23369 100644
--- a/chrome/browser/media_galleries/media_scan_manager_unittest.cc
+++ b/chrome/browser/media_galleries/media_scan_manager_unittest.cc
@@ -190,7 +190,8 @@ class MediaScanManagerTest : public MediaScanManagerObserver,
   }
 
   void StartScan() {
-    media_scan_manager_->StartScan(profile_.get(), extension_->id());
+    media_scan_manager_->StartScan(profile_.get(), extension_,
+                                   true /* user_gesture */);
   }
 
   MediaGalleriesPreferences* gallery_prefs() {
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 8290853..af9398c 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -2431,6 +2431,9 @@ const char kMediaGalleriesUniqueId[] = "media_galleries.gallery_id";
 const char kMediaGalleriesRememberedGalleries[] =
     "media_galleries.remembered_galleries";
 
+// The last time a media scan completed.
+const char kMediaGalleriesLastScanTime[] = "media_galleries.last_scan_time";
+
 #if defined(USE_ASH)
 // |kShelfAlignment| and |kShelfAutoHideBehavior| have a local variant. The
 // local variant is not synced and is used if set. If the local variant is not
diff --git a/chrome/common/pref_names.h b/chrome/common/pref_names.h
index 39b59b2..06bbaca 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -836,6 +836,7 @@ extern const char kComponentUpdaterState[];
 
 extern const char kMediaGalleriesUniqueId[];
 extern const char kMediaGalleriesRememberedGalleries[];
+extern const char kMediaGalleriesLastScanTime[];
 
 #if defined(USE_ASH)
 extern const char kShelfAlignment[];