Add support for taking partial screenshot using touch

ash/wm/partial_screenshot_view.h

Index: ash/wm/partial_screenshot_view.h
diff --git a/ash/wm/partial_screenshot_view.h b/ash/wm/partial_screenshot_view.h
index 19d21d35c0d4ec33af58aa3773d5c334baa4b412..aac411ea13f90b2a92c4462793ec3cdd3efb4eb4 100644
--- a/ash/wm/partial_screenshot_view.h
+++ b/ash/wm/partial_screenshot_view.h
@@ -5,8 +5,11 @@
 #ifndef ASH_WM_PARTIAL_SCREENSHOT_VIEW_H_
 #define ASH_WM_PARTIAL_SCREENSHOT_VIEW_H_
 
+#include <vector>
+
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
 #include "ui/gfx/point.h"
 #include "ui/views/widget/widget_delegate.h"
 
@@ -23,9 +26,13 @@ class ScreenshotDelegate;
 class ASH_EXPORT PartialScreenshotView : public views::WidgetDelegateView {
  public:
   // Starts the UI for taking partial screenshot; dragging to select a region.
-  static void StartPartialScreenshot(ScreenshotDelegate* screenshot_delegate);
+  static std::vector<PartialScreenshotView*>
+      StartPartialScreenshot(ScreenshotDelegate* screenshot_delegate);
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(PartialScreenshotViewTest, BasicMouse);
+  FRIEND_TEST_ALL_PREFIXES(PartialScreenshotViewTest, BasicTouch);
+
   class OverlayDelegate;
 
   PartialScreenshotView(OverlayDelegate* overlay_delegate,