Introduce the ENABLE_BROWSER_CDMS macro.

content/content_renderer.gypi

Index: content/content_renderer.gypi
diff --git a/content/content_renderer.gypi b/content/content_renderer.gypi
index 284ead3288b95804ddd2f347d3714f2afec0eeca..9b1c8f94360d61328071d6156534954fb746c48a 100644
--- a/content/content_renderer.gypi
+++ b/content/content_renderer.gypi
@@ -253,10 +253,6 @@
       'renderer/media/crypto/ppapi_decryptor.h',
       'renderer/media/crypto/proxy_decryptor.cc',
       'renderer/media/crypto/proxy_decryptor.h',
-      'renderer/media/crypto/proxy_media_keys.cc',
-      'renderer/media/crypto/proxy_media_keys.h',
-      'renderer/media/crypto/renderer_cdm_manager.cc',
-      'renderer/media/crypto/renderer_cdm_manager.h',
       'renderer/media/media_stream_audio_level_calculator.cc',
       'renderer/media/media_stream_audio_level_calculator.h',
       'renderer/media/media_stream_audio_renderer.cc',
@@ -824,6 +820,14 @@
         'renderer/media/crypto/ppapi_decryptor.h',
       ],
     }],
+    ['enable_browser_cdms==1', {
+      'sources': [
+        'renderer/media/crypto/proxy_media_keys.cc',
+        'renderer/media/crypto/proxy_media_keys.h',
+        'renderer/media/crypto/renderer_cdm_manager.cc',
+        'renderer/media/crypto/renderer_cdm_manager.h',
+      ],
+    }],
   ],
   'target_conditions': [
     ['OS=="android"', {