Don't destroy a window's buffers when moving it

Change-Id: Ib08608373ae4299639c1b157421ba633e4293446
diff --git a/core/java/android/view/WindowManager.java b/core/java/android/view/WindowManager.java
index fb31e7d..96c1512 100644
--- a/core/java/android/view/WindowManager.java
+++ b/core/java/android/view/WindowManager.java
@@ -1252,7 +1252,11 @@
         public static final int INPUT_FEATURES_CHANGED = 1<<15;
         /** {@hide} */
         public static final int PRIVATE_FLAGS_CHANGED = 1<<16;
-    
+        /** {@hide} */
+        public static final int BUFFER_CHANGED = 1<<17;
+        /** {@hide} */
+        public static final int EVERYTHING_CHANGED = 0xffffffff;
+
         // internal buffer to backup/restore parameters under compatibility mode.
         private int[] mCompatibilityParamsBackup = null;
         
@@ -1261,11 +1265,11 @@
     
             if (width != o.width) {
                 width = o.width;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (height != o.height) {
                 height = o.height;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (x != o.x) {
                 x = o.x;
@@ -1277,19 +1281,19 @@
             }
             if (horizontalWeight != o.horizontalWeight) {
                 horizontalWeight = o.horizontalWeight;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (verticalWeight != o.verticalWeight) {
                 verticalWeight = o.verticalWeight;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (horizontalMargin != o.horizontalMargin) {
                 horizontalMargin = o.horizontalMargin;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (verticalMargin != o.verticalMargin) {
                 verticalMargin = o.verticalMargin;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (type != o.type) {
                 type = o.type;
@@ -1297,7 +1301,7 @@
             }
             if (flags != o.flags) {
                 flags = o.flags;
-                changes |= FLAGS_CHANGED;
+                changes |= FLAGS_CHANGED | BUFFER_CHANGED;
             }
             if (privateFlags != o.privateFlags) {
                 privateFlags = o.privateFlags;
@@ -1309,11 +1313,11 @@
             }
             if (gravity != o.gravity) {
                 gravity = o.gravity;
-                changes |= LAYOUT_CHANGED;
+                changes |= LAYOUT_CHANGED | BUFFER_CHANGED;
             }
             if (format != o.format) {
                 format = o.format;
-                changes |= FORMAT_CHANGED;
+                changes |= FORMAT_CHANGED | BUFFER_CHANGED;
             }
             if (windowAnimations != o.windowAnimations) {
                 windowAnimations = o.windowAnimations;
@@ -1352,7 +1356,7 @@
     
             if (screenOrientation != o.screenOrientation) {
                 screenOrientation = o.screenOrientation;
-                changes |= SCREEN_ORIENTATION_CHANGED;
+                changes |= SCREEN_ORIENTATION_CHANGED | BUFFER_CHANGED;
             }
 
             if (systemUiVisibility != o.systemUiVisibility