[cr140][Android] Fixed close button at Rewards custom tab (#30812)

Fixed close button at Rewards custom tab

Resolves https://github.com/brave/brave-browser/issues/48678

Chromium change probably:
https://source.chromium.org/chromium/chromium/src/+/10303af4b9ba8510d05ca130a1545f0b303a2721

	Pad snackbars in SettingsActivity when edge-to-edge

	SettingsActivity creates the SnackbarManager with a parent view of the android.R.id.content, which is an issue when drawing edge-to-edge, since that base content view will be drawing underneath the system bars.

	This change adds #getContentView() to ChromeBaseAppCompatActivity, which will return the proper content view for the activity.

	Before:
	https://screenshot.googleplex.com/6wrywD2fGvLCbMA.png

	After:
	https://screenshot.googleplex.com/9wwkQ4GRnUTUNA8.png

	Bug: 398937046
	Change-Id: Ibfcebff816a8f19f091e299ff581aa3188f32afa
	Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6302322

android/java/org/chromium/chrome/browser/customtabs/FullScreenCustomTabActivity.java

@@ -88,7 +88,7 @@ public class FullScreenCustomTabActivity extends CustomTabActivity {
         layoutParams.gravity = Gravity.TOP | Gravity.START;
         layoutParams.setMargins(CLOSE_BUTTON_MARGIN, CLOSE_BUTTON_MARGIN, 0, 0);
 
-        ViewGroup parentView = findViewById(android.R.id.content);
+        ViewGroup parentView = getContentView();
         ImageView closeImg = new ImageView(FullScreenCustomTabActivity.this);
         closeImg.setPadding(
                 CLOSE_BUTTON_PADDING,