[Contextual Page Actions] Fixed crash on action chip transition

This CL fixes a null pointer exception when trying to post a task on an
OptionalButtonView instance that has been detached. This happens when
we finish the action chip expansion animation and we try to schedule
the collapse animation.

Bug: 1383559
Change-Id: I6fded66cab4f36368606f0469ccbc89586c0ea53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4022030
Commit-Queue: Salvador Guerrero Ramos <salg@google.com>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1070604}

chrome/browser/ui/android/toolbar/java/src/org/chromium/chrome/browser/toolbar/optional_button/OptionalButtonView.java

@@ -36,6 +36,7 @@
 
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.Callback;
+import org.chromium.base.ThreadUtils;
 import org.chromium.base.supplier.BooleanSupplier;
 import org.chromium.chrome.browser.toolbar.ButtonData;
 import org.chromium.chrome.browser.toolbar.ButtonData.ButtonSpec;
@@ -71,6 +72,7 @@ class OptionalButtonView extends FrameLayout implements TransitionListener {
     private int mBackgroundColorFilter;
     private Runnable mOnBeforeHideTransitionCallback;
     private Callback<Transition> mFakeBeginTransitionForTesting;
+    private Handler mHandler;
     private Handler mHandlerForTesting;
 
     private @State int mState;
@@ -296,7 +298,11 @@ public Handler getHandler() {
             return mHandlerForTesting;
         }
 
-        return super.getHandler();
+        if (mHandler == null) {
+            mHandler = new Handler(ThreadUtils.getUiThreadLooper());
+        }
+
+        return mHandler;
     }
 
     @Override