Add bookmarks search activity to browser.

This activity is never started from the browser. Its purpose
is to provide bookmark suggestions to global search (through
its searchable meta-data), and to handle the intents produced
by clicking such suggestions.
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index c67cc97..ace5750 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -176,6 +176,19 @@
                   android:theme="@android:style/Theme.Dialog">
         </activity>
 
+        <activity android:name="BookmarkSearch"
+                  android:label="@string/bookmarks_search"
+                  android:stateNotNeeded="true"
+                  android:theme="@android:style/Theme.NoDisplay"
+                  android:excludeFromRecents="true">
+            <intent-filter>
+                <action android:name="android.intent.action.SEARCH" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+            <meta-data android:name="android.app.searchable"
+                    android:resource="@xml/bookmarks_searchable" />
+        </activity>
+
         <service android:name="GearsDialogService"
                  android:process=":dialog"
                  android:exported="false">