graphics: add composer tests to VTS

Test: vts-tradefed run vts -m HalGraphicsComposerHidlTargetTest
Change-Id: I2e695787865d3bb855076acae18fa135064036ab
diff --git a/graphics/composer/2.1/IComposer.hal b/graphics/composer/2.1/IComposer.hal
index 771fc7d..553a537 100644
--- a/graphics/composer/2.1/IComposer.hal
+++ b/graphics/composer/2.1/IComposer.hal
@@ -53,6 +53,9 @@
      *
      * @return capabilities is a list of supported capabilities.
      */
+    @entry
+    @exit
+    @callflow(next="*")
     getCapabilities() generates (vec<Capability> capabilities);
 
     /*
@@ -61,6 +64,9 @@
      *
      * @return debugInfo is a string of debug information.
      */
+    @entry
+    @exit
+    @callflow(next="*")
     dumpDebugInfo() generates (string debugInfo);
 
     /*
@@ -73,5 +79,7 @@
      *         NO_RESOURCES when no more client can be created currently.
      * @return client is the newly created client.
      */
+    @entry
+    @callflow(next="*")
     createClient() generates (Error error, IComposerClient client);
 };