Fix drag bug.

Previous assumption -- that the drag window was defined at time of
DragState construction -- was false. The window, and hence the
Display, is not known until performDrag. This change delays assigning
DragState.mDisplayContent until the window/Display is known.

Fixes bug 7028203.

Change-Id: I5799005652c484ff0c45ab340ce3b9e4b784883e

Author: Craig Mautner

services/java/com/android/server/wm/DragState.java

@@ -71,12 +71,6 @@ class DragState {
         mFlags = flags;
         mLocalWin = localWin;
         mNotifiedWindows = new ArrayList<WindowState>();
-        WindowState win = service.mWindowMap.get(token);
-        if (win != null) {
-            mDisplayContent = win.mDisplayContent;
-        } else {
-            Slog.e(WindowManagerService.TAG, "No window associated with token");
-        }
     }
 
     void reset() {
@@ -92,7 +86,11 @@ void reset() {
         mNotifiedWindows = null;
     }
 
-    void register() {
+    /**
+     * @param displayContent The display parameters associated with the window being dragged.
+     */
+    void register(DisplayContent displayContent) {
+        mDisplayContent = displayContent;
         if (WindowManagerService.DEBUG_DRAG) Slog.d(WindowManagerService.TAG, "registering drag input channel");
         if (mClientChannel != null) {
             Slog.e(WindowManagerService.TAG, "Duplicate register of drag input channel");

services/java/com/android/server/wm/Session.java

@@ -280,7 +280,7 @@ public boolean performDrag(IWindow window, IBinder dragToken,
             // !!! FIXME: put all this heavy stuff onto the mH looper, as well as
             // the actual drag event dispatch stuff in the dragstate
 
-            mService.mDragState.register();
+            mService.mDragState.register(callingWin.mDisplayContent);
             mService.mInputMonitor.updateInputWindowsLw(true /*force*/);
             if (!mService.mInputManager.transferTouchFocus(callingWin.mInputChannel,
                     mService.mDragState.mServerChannel)) {