Improve query performance

[ Merge of http://go/wvgerrit/15780 ]

Android mediaDrm allows callers to serially query status information through a
property API. CDM however retrieves all status information in a map and
filters out all but the relevent one. This leads to delays in Netflix app
startup. Rewriting the CDM interface to return only the queried value.

b/24181894

Change-Id: Ie9ed6288524e3a7e03b83aa55ef3531dd52a0dfb

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -100,7 +100,8 @@ class CdmEngine {
 
   // Query system information
   virtual CdmResponseType QueryStatus(SecurityLevel security_level,
-                                      CdmQueryMap* info);
+                                      const std::string& key,
+                                      std::string* value);
 
   // Query session information
   virtual CdmResponseType QuerySessionStatus(const CdmSessionId& session_id,