public Builder setCustomItems(ArrayList<BrowserActionItem> items) {
            if (items.size() > MAX_CUSTOM_ITEMS) {
                throw new IllegalStateException(
                        "Exceeded maximum toolbar item count of " + MAX_CUSTOM_ITEMS);
            }
            for (int i = 0; i < items.size(); i++) {
                if (TextUtils.isEmpty(items.get(i).getTitle())
                        || items.get(i).getAction() == null) {
                    throw new IllegalArgumentException(
                            "Custom item should contain a non-empty title and non-null intent.");
                } else {
                    mMenuItems.add(getBundleFromItem(items.get(i)));
                    if (items.get(i).getIconUri() != null) {
                        mImageUris.add(items.get(i).getIconUri());
                    }
                }
            }
            return this;
        }
Sets the custom items list.
Only maximum MAX_CUSTOM_ITEMS custom items are allowed,
otherwise throws an {@link IllegalStateException}.
@param items The list of {@link BrowserActionItem} for custom items.
customtabs/src/android/support/customtabs/browseractions/BrowserActionsIntent.java