Allow taking screen shot of a non child window which has delegate to paint.

ash/test/test_screenshot_delegate.cc

Index: ash/test/test_screenshot_delegate.cc
diff --git a/ash/test/test_screenshot_delegate.cc b/ash/test/test_screenshot_delegate.cc
index a5d86ae250e26f46e601f27828d2f013834c891b..6a11b9f4a87df71475f2c166449e0c4985c54270 100644
--- a/ash/test/test_screenshot_delegate.cc
+++ b/ash/test/test_screenshot_delegate.cc
@@ -10,8 +10,8 @@ namespace test {
 TestScreenshotDelegate::TestScreenshotDelegate()
     : handle_take_screenshot_count_(0),
       handle_take_partial_screenshot_count_(0),
-      handle_take_window_screenshot_count_(0),
-      can_take_screenshot_(true) {
+      can_take_screenshot_(true),
+      selected_window_(nullptr) {
 }
 
 TestScreenshotDelegate::~TestScreenshotDelegate() {
@@ -28,12 +28,18 @@ void TestScreenshotDelegate::HandleTakePartialScreenshot(
 }
 
 void TestScreenshotDelegate::HandleTakeWindowScreenshot(aura::Window* window) {
-  handle_take_window_screenshot_count_++;
+  selected_window_ = window;
 }
 
 bool TestScreenshotDelegate::CanTakeScreenshot() {
   return can_take_screenshot_;
 }
 
+const aura::Window* TestScreenshotDelegate::GetSelectedWindowAndReset() {
+  aura::Window* result = selected_window_;
+  selected_window_ = nullptr;
+  return result;
+}
+
 }  // namespace test
 }  // namespace ash