Keep reference to CDM to avoid it's premature destruction

media/blink/webcontentdecryptionmodule_impl.h

Index: media/blink/webcontentdecryptionmodule_impl.h
diff --git a/media/blink/webcontentdecryptionmodule_impl.h b/media/blink/webcontentdecryptionmodule_impl.h
index 989b4a08cbeee174e81460227a4a5a09f731b6fc..306f61adf23072ffa83565fe3d9dc05e4a0d7143 100644
--- a/media/blink/webcontentdecryptionmodule_impl.h
+++ b/media/blink/webcontentdecryptionmodule_impl.h
@@ -53,10 +53,13 @@ class MEDIA_BLINK_EXPORT WebContentDecryptionModuleImpl
       blink::WebContentDecryptionModuleResult result) override;
 
   // Returns the CdmContext associated with this CDM, which must not be nullptr.
-  // TODO(jrummell): Figure out lifetimes, as WMPI may still use the decryptor
-  // after WebContentDecryptionModule is freed. http://crbug.com/330324
+  // Caller should keep a reference using GetCdmAdapterReference() to keep the
+  // CDM alive if necessary.
   CdmContext* GetCdmContext();
 
+  // Returns a reference to this CDM adapter.
+  CdmSessionAdapter* GetCdmAdapterReference();

[xhwang, 2016/10/07 05:02:14]

This returns a raw pointer, not a reference... Ah, CdmSessionAdapter is
refcounted. But usually for refcounted object, we put it in a scoped_refptr
immediately after it's created, and then we pretty much should never use the raw
pointer anywhere.

Actually, instead of letting WMPI hold a ref of the CdmSessionAdapter, can we
just let WIMPI hold a ref of the |cdm_|? That'll be consistent with AVDA and
MojoRendererService. Please see the comment here:

https://cs.chromium.org/chromium/src/media/base/media_keys.h?rcl=0&l=45

[jrummell, 2016/10/07 20:15:30]

Done.

+
  private:
   friend CdmSessionAdapter;