Widevine Metrics System

This change is the complete Widevine metrics system. It will
measure and record runtime information about what is happening
in the CDM - such as errors and throughput.

Bug: 33745339
Bug: 26027857
Change-Id: Ic9a82074f1e2b72c72d751b235f8ae361232787d

libwvdrmengine/cdm/core/test/license_unittest.cpp

@@ -79,6 +79,7 @@ const std::string kLicenseRequestSignature = a2bs_hex(
 
 class MockCryptoSession : public CryptoSession {
  public:
+  MockCryptoSession() : CryptoSession(NULL) { }
   MOCK_METHOD0(IsOpen, bool());
   MOCK_METHOD1(GenerateRequestId, bool(std::string*));
   MOCK_METHOD1(UsageInformationSupport, bool(bool*));