Move all wallpaper file loading and decoding from DesktopBackgroundController to WallpaperManager.

ash/test/ash_test_helper.cc

Index: ash/test/ash_test_helper.cc
diff --git a/ash/test/ash_test_helper.cc b/ash/test/ash_test_helper.cc
index f66c6ce3907635d48efa4624f8a965057f408a22..9e82252aa75f4a7f9cfc8bfb9a61f3454d793fe5 100644
--- a/ash/test/ash_test_helper.cc
+++ b/ash/test/ash_test_helper.cc
@@ -147,5 +147,23 @@ aura::Window* AshTestHelper::CurrentContext() {
   return root_window;
 }
 
+// static
+bool AshTestHelper::SupportsMultipleDisplays() {
+#if defined(OS_WIN)
+  return base::win::GetVersion() < base::win::VERSION_WIN8;
+#else
+  return true;
+#endif
+}
+
+// static
+bool AshTestHelper::SupportsHostWindowResize() {
+#if defined(OS_WIN)
+  return base::win::GetVersion() < base::win::VERSION_WIN8;
+#else
+  return true;
+#endif
+}
+
 }  // namespace test
 }  // namespace ash