Minor updates to EME-related comments

Change-Id: I8373457c77dfa0ebacb02e8aeaa8de8b2a328eb3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1841670Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Commit-Queue: David Dorwin <ddorwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703431}

media/base/key_system_properties.h

@@ -33,7 +33,10 @@ class MEDIA_EXPORT KeySystemProperties {
   // Returns the codecs supported by this key system.
   virtual SupportedCodecs GetSupportedCodecs() const = 0;
 
-  // Returns the codecs with hardware-secure support in this key system.
+  // Returns the codecs can be used with the hardware-secure mode of this key
+  // system. The codecs may be supported with any hardware-based robustness
+  // level. Other parts of the code handle reporting appropriate levels of
+  // robustness support for audio and video.
   virtual SupportedCodecs GetSupportedHwSecureCodecs() const;
 
   // Returns the configuration rule for supporting a robustness requirement.

media/base/key_systems.cc

@@ -686,9 +686,9 @@ EmeConfigRule KeySystemsImpl::GetContentTypeConfigRule(
       return EmeConfigRule::NOT_SUPPORTED;
     }
 
-    // Check whether the codec supports a hardware-secure mode. The goal is to
-    // prevent mixing of non-hardware-secure codecs with hardware-secure codecs,
-    // since the mode is fixed at CDM creation.
+    // Check whether the codec supports a hardware-secure mode (any level). The
+    // goal is to prevent mixing of non-hardware-secure codecs with
+    // hardware-secure codecs, since the mode is fixed at CDM creation.
     //
     // Because the check for regular codec support is early-exit, we don't have
     // to consider codecs that are only supported in hardware-secure mode. We

media/filters/decrypting_demuxer_stream.h

@@ -40,7 +40,7 @@ class MEDIA_EXPORT DecryptingDemuxerStream : public DemuxerStream {
   // Cancels all pending operations immediately and fires all pending callbacks.
   ~DecryptingDemuxerStream() override;
 
-  // |steram| must be encrypted and |cdm_context| must be non-null.
+  // |stream| must be encrypted and |cdm_context| must be non-null.
   void Initialize(DemuxerStream* stream,
                   CdmContext* cdm_context,
                   const PipelineStatusCB& status_cb);

media/gpu/windows/d3d11_decryptor.cc

@@ -142,7 +142,7 @@ D3D11Decryptor::~D3D11Decryptor() {}
 
 void D3D11Decryptor::RegisterNewKeyCB(StreamType stream_type,
                                       const NewKeyCB& new_key_cb) {
-  // TODO(xhwang): Use RegisterNewKeyCB() on CdmContext, and remove
+  // TODO(crbug.com/821288): Use RegisterNewKeyCB() on CdmContext, and remove
   // RegisterNewKeyCB from Decryptor interface.
   NOTREACHED();
 }