aura: Fix a couple of drag drop issues:

ash/drag_drop/drag_drop_controller.cc

Index: ash/drag_drop/drag_drop_controller.cc
diff --git a/ash/drag_drop/drag_drop_controller.cc b/ash/drag_drop/drag_drop_controller.cc
index dd8a0971a638a1b75858c277737fc10b2ab34cc8..423e1384692ddb04a0e10b91491476918cb3dca7 100644
--- a/ash/drag_drop/drag_drop_controller.cc
+++ b/ash/drag_drop/drag_drop_controller.cc
@@ -32,6 +32,12 @@ using aura::RootWindow;
 namespace {
 const base::TimeDelta kDragDropAnimationDuration =
     base::TimeDelta::FromMilliseconds(250);
+
+void UnlockAndSwitchCursor(gfx::NativeCursor new_cursor) {
+  ash::Shell::GetInstance()->cursor_manager()->UnlockCursor();

[sky, 2012/08/02 16:26:42]

Unlock/Lock decrement/increment a count. So, it's entirely possible this won't
set the cursor.

[varunjain, 2012/08/02 17:29:52]

I have moved the cursor locking to the RootWindow.
I wish there was some nicer way to use the cursor manager's locking
functionality :(
Do you have any other idea?

+  ash::Shell::GetInstance()->cursor_manager()->SetCursor(new_cursor);
+  ash::Shell::GetInstance()->cursor_manager()->LockCursor();
+}
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -64,6 +70,7 @@ int DragDropController::StartDragAndDrop(const ui::OSExchangeData& data,
   if (capture_window)
     capture_window->ReleaseCapture();
   drag_drop_in_progress_ = true;
+  ash::Shell::GetInstance()->cursor_manager()->LockCursor();
 
   drag_data_ = &data;
   drag_operation_ = operation;
@@ -128,7 +135,7 @@ void DragDropController::DragUpdate(aura::Window* target,
         cursor = ui::kCursorAlias;
       else if (op & ui::DragDropTypes::DRAG_MOVE)
         cursor = ui::kCursorMove;
-      ash::Shell::GetInstance()->cursor_manager()->SetCursor(cursor);
+      UnlockAndSwitchCursor(cursor);
     }
   }
 
@@ -141,7 +148,7 @@ void DragDropController::DragUpdate(aura::Window* target,
 
 void DragDropController::Drop(aura::Window* target,
                               const aura::LocatedEvent& event) {
-  ash::Shell::GetInstance()->cursor_manager()->SetCursor(ui::kCursorPointer);
+  UnlockAndSwitchCursor(ui::kCursorPointer);
   aura::client::DragDropDelegate* delegate = NULL;
 
   // We must guarantee that a target gets a OnDragEntered before Drop. WebKit
@@ -170,7 +177,7 @@ void DragDropController::Drop(aura::Window* target,
 }
 
 void DragDropController::DragCancel() {
-  ash::Shell::GetInstance()->cursor_manager()->SetCursor(ui::kCursorPointer);
+  UnlockAndSwitchCursor(ui::kCursorPointer);
 
   // |drag_window_| can be NULL if we have just started the drag and have not
   // received any DragUpdates, or, if the |drag_window_| gets destroyed during
@@ -211,9 +218,6 @@ bool DragDropController::PreHandleMouseEvent(aura::Window* target,
     case ui::ET_MOUSE_RELEASED:
       Drop(target, *event);
       break;
-    case ui::ET_MOUSE_EXITED:
-      DragCancel();
-      break;
     default:
       // We could reach here if the user drops outside the root window.
       // We could also reach here because RootWindow may sometimes generate a
@@ -292,6 +296,8 @@ void DragDropController::Cleanup() {
   drag_window_ = NULL;
   drag_data_ = NULL;
   drag_drop_in_progress_ = false;
+  if (ash::Shell::GetInstance()->cursor_manager()->is_cursor_locked())
+    ash::Shell::GetInstance()->cursor_manager()->UnlockCursor();
 }
 
 }  // namespace internal