Implement random wallpaper feature

BUG=120217
TEST=Go to set wallpaper overlay in settings page, check the "I'm feeling
lucky" checkbox. Sign out and sign in a couple of times, verify if the
wallpaper is random.

Review URL: https://chromiumcodereview.appspot.com/10302016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@135862 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 9 insertions, 0 deletions

diff --git a/ash/desktop_background/desktop_background_resources.cc b/ash/desktop_background/desktop_background_resources.cc
index 5b7d07f..e5cf675 100644
--- a/ash/desktop_background/desktop_background_resources.cc
+++ b/ash/desktop_background/desktop_background_resources.cc
@@ -229,12 +229,14 @@ const int kInvalidWallpaperIndex = -1;
 // of the array are really hacky.
 #if defined(GOOGLE_CHROME_BUILD)
 const int kDefaultWallpaperIndex = 16; // IDR_AURA_WALLPAPERS_3_URBAN0
+const int kLastRandomWallpaperIndex = 19; // The first 20 are random.
 const int kGuestWallpaperIndex = 26;   // IDR_AURA_WALLPAPERS_5_GRADIENT6
 #else
 // Set default wallpaper to the grey background for faster wallpaper loading
 // time in browser tests. Otherwise, some of the tests will finish before
 // wallpaper loaded and cause crashes.
 const int kDefaultWallpaperIndex = 6;  // IDR_AURA_WALLPAPERS_5_GRADIENT5
+const int kLastRandomWallpaperIndex = 8;
 const int kGuestWallpaperIndex = kDefaultWallpaperIndex;
 #endif
 
@@ -256,6 +258,12 @@ int GetGuestWallpaperIndex() {
   return std::min(kGuestWallpaperIndex, kDefaultWallpaperCount - 1);
 }
 
+int GetRandomWallpaperIndex() {
+  DCHECK(kLastRandomWallpaperIndex < kDefaultWallpaperCount);
+  return base::RandInt(0,
+      std::min(kLastRandomWallpaperIndex, kDefaultWallpaperCount - 1));
+}
+
 int GetWallpaperCount() {
   return kDefaultWallpaperCount;
 }
diff --git a/ash/desktop_background/desktop_background_resources.h b/ash/desktop_background/desktop_background_resources.h
index 5a0391d..19f23d0 100644
--- a/ash/desktop_background/desktop_background_resources.h
+++ b/ash/desktop_background/desktop_background_resources.h
@@ -31,6 +31,7 @@ struct ASH_EXPORT WallpaperInfo {
 ASH_EXPORT int GetInvalidWallpaperIndex();
 ASH_EXPORT int GetDefaultWallpaperIndex();
 ASH_EXPORT int GetGuestWallpaperIndex();
+ASH_EXPORT int GetRandomWallpaperIndex();
 ASH_EXPORT int GetWallpaperCount();
 ASH_EXPORT const WallpaperInfo& GetWallpaperInfo(int index);