[android] Support full-screen on cobalt_apk and fix URL logic on launch

1. Set URL filed to GONE to support full-screen video on ATV.
2. Refactor setting URL logic on launching Cobalt.apk.

b/362837382
b/376148547

cobalt/android/apk/app/src/main/java/dev/cobalt/coat/CobaltActivity.java

@@ -32,6 +32,7 @@
 import android.view.ViewGroup.LayoutParams;
 import android.view.ViewParent;
 import android.widget.FrameLayout;
+import android.widget.LinearLayout;
 import dev.cobalt.media.MediaCodecCapabilitiesLogger;
 import dev.cobalt.media.VideoSurfaceView;
 import dev.cobalt.util.DisplayUtil;
@@ -143,10 +144,7 @@ protected void createContent(final Bundle savedInstanceState) {
       mWindowAndroid.setAnimationPlaceholderView(
               mShellManager.getContentViewRenderView().getSurfaceView());
 
-      // TODO(cobalt, b/376148547): set Chrobalt initial url and remove this function.
-      if (mStartupUrl.isEmpty()) {
-          mStartupUrl = getUrlFromIntent(getIntent());
-      }
+      mStartupUrl = getUrlFromIntent(getIntent());
       if (!TextUtils.isEmpty(mStartupUrl)) {
           mShellManager.setStartupUrl(Shell.sanitizeUrl(mStartupUrl));
       }
@@ -160,7 +158,7 @@ protected void createContent(final Bundle savedInstanceState) {
                   new BrowserStartupController.StartupCallback() {
                       @Override
                       public void onSuccess() {
-                          finishInitialization(savedInstanceState);
+                          finishCobaltInitialization();
                       }
 
                       @Override
@@ -240,9 +238,15 @@ protected void shellHandleIntent(Intent intent) {
       }
   }
 
-  // TODO(cobalt, b/376148547): set Chrobalt initial url and remove this function.
-  protected void setStartupUrl(String url) {
-      mStartupUrl = url;
+  private void finishCobaltInitialization() {
+      mShellManager.launchShell("https://www.youtube.com/tv");
+
+      toggleFullscreenMode(true);
+  }
+
+  protected void toggleFullscreenMode(boolean enterFullscreen) {
+    LinearLayout toolBar = (LinearLayout) findViewById(R.id.toolbar);
+    toolBar.setVisibility(enterFullscreen ? View.GONE : View.VISIBLE);
   }
 
   // Initially copied from ContentShellActiviy.java
@@ -322,7 +326,6 @@ protected void onCreate(Bundle savedInstanceState) {
       getStarboardBridge().handleDeepLink(startDeepLink);
     }
 
-    setStartupUrl("https://www.youtube.com/tv");
     super.onCreate(savedInstanceState);
     createContent(savedInstanceState);