Set text direction in promo dialog to locale mode

The text direction is ltr when there is a non-translatable english
word in the rtl language text. Set locale mode so that the text
direction and alignment are determined by the system language
text direction and alignment.

Bug: 1107254
Change-Id: I05c318479e064204e49591ff9861184fabea1ded
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307480Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
Commit-Queue: Lijin Shen <lazzzis@google.com>
Cr-Commit-Position: refs/heads/master@{#790004}

components/browser_ui/widget/android/java/res/layout/promo_dialog_layout.xml

@@ -63,6 +63,7 @@
                         android:id="@+id/header"
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
+                        android:textDirection="locale"
                         android:layout_marginTop="@dimen/dialog_header_margin"
                         android:layout_marginBottom="@dimen/dialog_header_margin"
                         android:textAppearance="@style/TextAppearance.Headline.Primary" />
@@ -71,6 +72,7 @@
                         android:id="@+id/subheader"
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
+                        android:textDirection="locale"
                         app:leading="@dimen/text_size_medium_leading"
                         style="@style/TextAppearance.TextMedium.Secondary" />
                 </org.chromium.components.browser_ui.widget.BoundedLinearLayout>