better scrolling in JS-less single-message conversation view

Allow simultaneous horizontal and vertical scrolling when the WebView is
embedded in a ScrollView by supplementally sending touch events to the
ScrollView when it normally wants to intercept AND the WebView handled
the touch. Touch interception happens as normal on any other child.

Bug: 8368615
Change-Id: I21f8721c673fd8146992b933d0c966d59c376795
diff --git a/res/layout/secure_conversation_view.xml b/res/layout/secure_conversation_view.xml
index da1dae3..26b4920 100644
--- a/res/layout/secure_conversation_view.xml
+++ b/res/layout/secure_conversation_view.xml
@@ -18,7 +18,7 @@
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
-    <ScrollView android:id="@+id/scroll_view"
+    <com.android.mail.browse.MessageScrollView android:id="@+id/scroll_view"
         android:layout_width="match_parent"
         android:layout_height="match_parent">
         <LinearLayout
@@ -37,18 +37,18 @@
                 android:layout_height="wrap_content"
                 android:layout_below="@id/conv_header" />
             <!-- base WebView layer -->
-            <WebView
+            <com.android.mail.browse.MessageWebView
                 android:id="@+id/webview"
                 android:layout_width="match_parent"
                 android:layout_height="0dp"
-                android:layout_weight="1.0"/>
+                android:layout_weight="1.0" />
             <include layout="@layout/conversation_message_footer"
                 android:id="@+id/message_footer"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:visibility="gone" />
         </LinearLayout>
-    </ScrollView>
+    </com.android.mail.browse.MessageScrollView>
 
     <include layout="@layout/conversation_load_spinner"/>