Move ENABLE_PEPPER_CDMS to a buildflag header.

components/cdm/renderer/external_clear_key_key_system_properties.h

Index: components/cdm/renderer/external_clear_key_key_system_properties.h
diff --git a/components/cdm/renderer/external_clear_key_key_system_properties.h b/components/cdm/renderer/external_clear_key_key_system_properties.h
index d0ed06fd875505452bb5b4c943734316c1dfa665..9b50b1a98e881bdc50ab80ab57eaa5c4d124f3d8 100644
--- a/components/cdm/renderer/external_clear_key_key_system_properties.h
+++ b/components/cdm/renderer/external_clear_key_key_system_properties.h
@@ -9,10 +9,11 @@
 
 #include "build/build_config.h"
 #include "media/base/key_system_properties.h"
+#include "ppapi/features/features.h"
 
 namespace cdm {
 
-#if defined(ENABLE_PEPPER_CDMS)
+#if BUILDFLAG(ENABLE_PEPPER_CDMS)
 extern const char kExternalClearKeyPepperType[];
 #endif
 
@@ -35,7 +36,7 @@ class ExternalClearKeyProperties : public media::KeySystemProperties {
       const override;
   media::EmeFeatureSupport GetPersistentStateSupport() const override;
   media::EmeFeatureSupport GetDistinctiveIdentifierSupport() const override;
-#if defined(ENABLE_PEPPER_CDMS)
+#if BUILDFLAG(ENABLE_PEPPER_CDMS)
   std::string GetPepperType() const override;
 #endif