[SharingHub] Make QrCode share tab a scroll view

Wrap the contents of the share tab (QrCode + Download button)
in a scroll view so everything can be seen on smaller devices.

Bug: 1105809
Change-Id: Iba3b85c5a6ef31beb24bb080a7b12942298a79cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2300232Reviewed-by: Tanya Gupta <tgupta@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788788}

chrome/browser/share/android/java/res/layout/qrcode_share_layout.xml

@@ -2,12 +2,16 @@
 <!-- Copyright 2019 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
-<LinearLayout
+<ScrollView
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/share_layout"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical">
+<LinearLayout
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical">
     <ImageView
         android:id="@+id/tab_line"
         android:layout_width="match_parent"
@@ -51,4 +55,5 @@
         android:layout_marginTop="30dp"
         android:text="@string/open_settings_button"
         style="@style/TextButton"/>
-</LinearLayout>
+  </LinearLayout>
+</ScrollView>