[web_view] Add hook to download prebuilt libwebkit.so

Change-Id: Ia714b3b3db2080e7a71052ad183dace0cd558dd0
diff --git a/web_view b/web_view
index e521461..af6e20a 100644
--- a/web_view
+++ b/web_view
@@ -28,5 +28,10 @@
              githooks="manifest/git-hooks"
              historydepth="1"/>
   </projects>
+  <hooks>
+    <hook name="download-libwebkit"
+          project="web_view"
+          action="scripts/download-libwebkit.sh"/>
+  </hooks>
 </manifest>