media: Add UMA to report CDM interface version being used

media/cdm/ppapi/ppapi_cdm_adapter.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/cdm/ppapi/ppapi_cdm_adapter.h"
 
 #include <string.h>
 
 #include "base/macros.h"
 #include "build/build_config.h"
@@ skipping 337 matching lines @@
   // The Pepper plugin will be staticly linked to the CDM, so pass the plugin's
   // CreateCdmInstance() to CdmWrapper.
   CdmWrapper* cdm = CdmWrapper::Create(::CreateCdmInstance, key_system.data(),
                                        key_system.size(), GetCdmHost, this);
 
   const std::string message = "CDM instance for " + key_system +
                               (cdm ? "" : " could not be") + " created.";
   DLOG_TO_CONSOLE(message);
   CDM_DLOG() << message;
 
+  if (cdm) {
+    pp::UMAPrivate uma_interface(this);
+
+    // The interface version is relatively small. So using normal histogram
+    // instead of a sparse histogram is okay. The following DCHECK asserts this.
+    PP_DCHECK(cdm->GetInterfaceVersion() <= 100);

[Ilya Sherman, 2016/08/23 02:35:32]

Please set the upper bound to something closer to 20.

[xhwang, 2016/08/23 19:07:14]

Done with 30, which will be enough for several years.

+    uma_interface.HistogramEnumeration(
+        "Media.EME.CdmInterfaceVersion", cdm->GetInterfaceVersion(),
+        // Sample value should always be less than the boundary. Hence use "+1".
+        // See the comment on HistogramEnumeration in ppb_uma_private.idl.
+        cdm::ContentDecryptionModule::kVersion + 1);
+  }
+
   return cdm;
 }
 
 void PpapiCdmAdapter::Initialize(uint32_t promise_id,
                                  const std::string& key_system,
                                  bool allow_distinctive_identifier,
                                  bool allow_persistent_state) {
   PP_DCHECK(!key_system.empty());
   PP_DCHECK(!cdm_);
 
@@ skipping 945 matching lines @@
 }  // namespace media
 
 namespace pp {
 
 // Factory function for your specialization of the Module object.
 Module* CreateModule() {
   return new media::PpapiCdmAdapterModule();
 }
 
 }  // namespace pp