Only refresh DISABLED_NO_THUMBNAIL when thumbnail changes

- Avoid refreshing all overlay content which happens too frequently

Bug: 193125090
Test: atest NexusLauncherTests:com.android.quickstep.TaplTestsQuickstep#testOverviewActions
Change-Id: Idcfe19a518e621c55574baae3bbe1378b7f3d08f

quickstep/src/com/android/quickstep/TaskOverlayFactory.java

@@ -182,6 +182,13 @@ public class TaskOverlayFactory implements ResourceBasedOverride {
             }
         }
 
+        /**
+         * Called when the current task's thumbnail has changed.
+         */
+        public void refreshActionVisibility(ThumbnailData thumbnail) {
+            getActionsView().updateDisabledFlags(DISABLED_NO_THUMBNAIL, thumbnail == null);
+        }
+
         /**
          * End rendering live tile in Overview.
          *

quickstep/src/com/android/quickstep/views/TaskThumbnailView.java

@@ -162,7 +162,9 @@ public class TaskThumbnailView extends View implements PluginListener<OverviewSc
             mBitmapShader = new BitmapShader(bm, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
             mPaint.setShader(mBitmapShader);
             updateThumbnailMatrix();
-            refreshOverlay();
+            if (mOverlayEnabled) {
+                getTaskOverlay().refreshActionVisibility(mThumbnailData);
+            }
         } else {
             mBitmapShader = null;
             mThumbnailData = null;