media: Add more logs in CdmAdapter

CdmAdapter is the host of the library CDM. To investigate CDM related
issues, especially subtle timing-related issues, it's better to have
better logging in CdmAdapter.

Bug: 883003

Change-Id: I13d5f34ea370f3802f8e8beff84e4c9df0dbd8ca
Reviewed-on: https://chromium-review.googlesource.com/1238823Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594101}

media/blink/new_session_cdm_result_promise.cc

@@ -68,6 +68,8 @@ NewSessionCdmResultPromise::~NewSessionCdmResultPromise() {
 }
 
 void NewSessionCdmResultPromise::resolve(const std::string& session_id) {
+  DVLOG(1) << __func__ << ": session_id = " << session_id;
+
   // |new_session_created_cb_| uses a WeakPtr<> and may not do anything
   // if the session object has been destroyed.
   SessionInitStatus status = SessionInitStatus::UNKNOWN_STATUS;
@@ -93,6 +95,9 @@ void NewSessionCdmResultPromise::resolve(const std::string& session_id) {
 void NewSessionCdmResultPromise::reject(CdmPromise::Exception exception_code,
                                         uint32_t system_code,
                                         const std::string& error_message) {
+  DVLOG(1) << __func__ << ": system_code = " << system_code
+           << ", error_message = " << error_message;
+
   MarkPromiseSettled();
   ReportCdmResultUMA(uma_name_,
                      ConvertCdmExceptionToResultForUMA(exception_code));