Sends signed provisioning request as query string instead of payload.

Bug: 8790775

Merge of https://widevine-internal-review.googlesource.com/#/c/5381/
from the Widevine CDM repository.

Change-Id: I749303eee8162f37982f6dd5d83b6cf254b96847

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -106,8 +106,8 @@ class CdmEngine : public TimerHandler {
   // Cancel all sessions
   bool CancelSessions();
   void CleanupProvisioningSession(const CdmSessionId& cdm_session_id);
-  void ComposeJsonRequest(const std::string& message,
-                          CdmProvisioningRequest* request);
+  void ComposeJsonRequestAsQueryString(const std::string& message,
+                                       CdmProvisioningRequest* request);
 
   bool ParseJsonResponse(const CdmProvisioningResponse& json_str,
                          const std::string& start_substr,