Remove the checksum/HMAC code from the decryptor.

media/base/decrypt_config.h

Index: media/base/decrypt_config.h
diff --git a/media/base/decrypt_config.h b/media/base/decrypt_config.h
index 669aa36bb1684ab04f6bfa74d332aa7800a08f85..be0bb4d61b1e51e6e22b8d399247a53eb7d50fb7 100644
--- a/media/base/decrypt_config.h
+++ b/media/base/decrypt_config.h
@@ -37,10 +37,7 @@ class MEDIA_EXPORT DecryptConfig {
   // |key_id| is the ID that references the decryption key for this sample.
   // |iv| is the initialization vector defined by the encrypted format.
   //   Currently |iv| must be 16 bytes as defined by WebM and ISO. Or must be
-  //   empty which signals to perform the integrity check on an unencrypted
-  //   frame as defined WebM.
-  // |checksum| is the hash value of the encrypted buffer. |checksum| is
-  //   defined by the encrypted format and may be NULL.
+  //   empty which signals an unencrypted frame.
   // |data_offset| is the amount of data that should be discarded from the
   //   head of the sample buffer before applying subsample information. A
   //   decrypted buffer will be shorter than an encrypted buffer by this amount.
@@ -48,17 +45,15 @@ class MEDIA_EXPORT DecryptConfig {
   //   described above. A decrypted buffer will be equal in size to the sum
   //   of the subsample sizes.
   //
-  // |data_offset| is applied after |checksum|, but before |subsamples|.
+  // |data_offset| is applied before |subsamples|.
   DecryptConfig(const std::string& key_id,
                 const std::string& iv,
-                const std::string& checksum,
                 const int data_offset,
                 const std::vector<SubsampleEntry>& subsamples);
   ~DecryptConfig();
 
   const std::string& key_id() const { return key_id_; }
   const std::string& iv() const { return iv_; }
-  const std::string& checksum() const { return checksum_; }
   int data_offset() const { return data_offset_; }
   const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; }
 
@@ -68,10 +63,8 @@ class MEDIA_EXPORT DecryptConfig {
   // Initialization vector.
   const std::string iv_;
 
-  // Checksum of the data to be verified before decrypting the data. This may
-  // be empty for some formats.
-  const std::string checksum_;
-
+  // TODO(fgalligan): Remove |data_offset_| if there is no plan to use it in
+  // the future.
   // Amount of data to be discarded before applying subsample information.
   const int data_offset_;