chromeos: converts DragImageViewTest to AshTestBase

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index 21eeea617cfa595d5f9b619d0cd136339f2269ce..6f4a493e63a64f7f6f6cc87cc0a7e828f058bff8 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <string>
 
+#include "ash/public/cpp/shell_window_ids.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/threading/thread.h"
@@ -91,6 +92,17 @@ class AshTestBase : public testing::Test {
       int container_id,
       const gfx::Rect& bounds);
 
+  // Creates a visible window in the appropriate container. If
+  // |bounds_in_screen| is empty the window is added to the primary root
+  // window, otherwise the window is added to the display matching
+  // |bounds_in_screen|. |shell_window_id| is the shell window id to give to
+  // the new window.
+  // TODO(sky): convert existing CreateTestWindow() functions into this one.

[msw, 2017/04/18 21:43:09]

aside q: Will returning a unique_ptr instead of a raw pointer change the window
destruction semantics for the numerous tests calling the existing functions?
(generally I think of tests simply allowing the window to be destroyed later on
via some TearDown mechanism, not via aura::Window destruction in the test
fixture body when the unique_ptr goes out of scope). I imagine this generally
won't be a problem, and a few cases can release the unique_ptr, but I'm just
curious about your thoughts.

[sky, 2017/04/18 22:03:02]

I actually haven't done a big analysis. I generally favor unique_ptr, event if
the callers do a release() as it's less error prone.

+  std::unique_ptr<aura::Window> CreateTestWindow(

[msw, 2017/04/18 21:43:09]

optional nit: order params to match CreateTestWindowInShellWithDelegateAndType;
that might ease some conversion later on.

[sky, 2017/04/18 22:03:02]

I went with this ordering based on looking at tests and seeing most wanting to
specify bounds, and then falling off in usage from there.

+      const gfx::Rect& bounds_in_screen = gfx::Rect(),
+      ui::wm::WindowType type = ui::wm::WINDOW_TYPE_NORMAL,
+      int shell_window_id = kShellWindowId_Invalid);
+
   // Versions of the functions in aura::test:: that go through our shell
   // StackingController instead of taking a parent.
   aura::Window* CreateTestWindowInShellWithId(int id);