Switch search to use the existing header.

Probably best to not try out any possible new design changes just yet.
Let's stick with what we have.

res/drawable/header_search_background.xml

@@ -1,13 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item>
-        <shape android:shape="rectangle" >
-            <solid android:color="@color/grey_200"/>
-        </shape>
-    </item>
-    <item android:top="1dp">
-        <shape android:shape="rectangle" >
-            <solid android:color="?attr/search_background" />
-        </shape>
-    </item>
-</layer-list>

res/layout/header_search_result.xml

@@ -1,13 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<TextView
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    style="@style/Base.TextAppearance.AppCompat.Body2"
-    android:orientation="vertical"
-    android:layout_width="match_parent"
-    android:layout_height="wrap_content"
-    android:padding="8dp"
-    android:background="@drawable/header_search_background"
-    tools:text="Conversations">
-
-</TextView>

src/org/thoughtcrime/securesms/search/SearchListAdapter.java

@@ -97,7 +97,7 @@ class SearchListAdapter extends    RecyclerView.Adapter<SearchListAdapter.Search
   @Override
   public HeaderViewHolder onCreateHeaderViewHolder(ViewGroup parent) {
     return new HeaderViewHolder(LayoutInflater.from(parent.getContext())
-                                              .inflate(R.layout.header_search_result, parent, false));
+                                              .inflate(R.layout.contact_selection_list_divider, parent, false));
   }
 
   @Override
@@ -199,7 +199,7 @@ class SearchListAdapter extends    RecyclerView.Adapter<SearchListAdapter.Search
 
     public HeaderViewHolder(View itemView) {
       super(itemView);
-      titleView = (TextView) itemView;
+      titleView = itemView.findViewById(R.id.label);
     }
 
     public void bind(int headerType) {