Support code coverage measurement for vts-staging-web plan

* To uplode code coverage measurement to staging dashboard.

Bug:110851162
Test: make vts
Change-Id: I0ccd9c28fe799dde12837f2b9480776a80415f22
diff --git a/tools/vts-tradefed/res/config/vts-staging-web.xml b/tools/vts-tradefed/res/config/vts-staging-web.xml
index 655cc3a..299ccc9 100644
--- a/tools/vts-tradefed/res/config/vts-staging-web.xml
+++ b/tools/vts-tradefed/res/config/vts-staging-web.xml
@@ -15,6 +15,7 @@
 -->
 <configuration description="VTS Staging Plan for VTS Dashboard">
   <include name="vts-base" />
+  <target_preparer class="com.android.tradefed.targetprep.VtsCoveragePreparer" />
   <option name="plan" value="vts" />
   <option name="test-tag" value="vts-star" />
   <option name="vts-plan-result:plan-name" value="vts-staging-web" />