[Chromecast] Toggle fragment visibility to avoid flash when attach or detach

Set cast fragment to invisible when detach from activity to avoid a flash of cast app view at the last frame

Bug: internal b/77214997

Change-Id: I18b11a8159f2d308dea6c3a8294b4059cbe1864a
Reviewed-on: https://chromium-review.googlesource.com/1023056
Commit-Queue: Zhiheng(Vincent) Li <vincentli@google.com>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553424}

chromecast/browser/android/apk/res/layout/cast_web_contents_activity.xml

@@ -7,7 +7,7 @@
 
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/web_contents_container"
-    android:background="#000000"
+    android:background="#FFFFFF"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:layout_weight="1">

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastWebContentsFragment.java

@@ -113,6 +113,9 @@ public class CastWebContentsFragment extends Fragment {
     public void onPause() {
         Log.d(TAG, "onPause");
         super.onPause();
+        // Set mFragmentRootView to invisible to avoid dismiss fragment animation -> activity back
+        // ground -> one frame of cast app UI -> acivity back ground
+        mFragmentRootView.setVisibility(View.INVISIBLE);
         mResumedState.reset();
     }
 
@@ -120,9 +123,19 @@ public class CastWebContentsFragment extends Fragment {
     public void onResume() {
         Log.d(TAG, "onResume");
         super.onResume();
+        // Delayed set mFragmentRootView to visible to avoid activity UI -> one frame of fragment
+        // background -> cast app rendered UI
+        mFragmentRootView.setVisibility(View.INVISIBLE);
+        mFragmentRootView.postDelayed(this ::setToVisible, 150);
         mResumedState.set(Unit.unit());
     }
 
+    private void setToVisible() {
+        if (isResumed()) {
+            mFragmentRootView.setVisibility(View.VISIBLE);
+        }
+    }
+
     @Override
     public void onStop() {
         Log.d(TAG, "onStop");