Reland "Refactor FrameDecryptorInterface::Decrypt to use new API."

This reverts commit 7dd83e2bf73a7f1746c5ee976939bf52e19fa8be.

Reason for revert: This wasn't the cause of the break. 

Original change's description:
> Revert "Refactor FrameDecryptorInterface::Decrypt to use new API."
> 
> This reverts commit 642aa81f7d5cc55d5b99e2abc51327eed9d40195.
> 
> Reason for revert: Speculative revert. The chromium roll is failing:
> https://ci.chromium.org/p/chromium/builders/try/linux-rel/64388
> But I can't figure out exactly what is failing, this looks suspecious.
> 
> Original change's description:
> > Refactor FrameDecryptorInterface::Decrypt to use new API.
> > 
> > This change refactors the FrameDecryptorInterface to use the new API. The new
> > API surface simply moves bytes_written to the return type and implements a
> > simple Status type.
> > 
> > Bug: webrtc:10512
> > Change-Id: I622c5d344d58e618853c94c2f691cf7c8fb73a36
> > Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131460
> > Reviewed-by: Steve Anton <steveanton@webrtc.org>
> > Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
> > Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
> > Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> > Commit-Queue: Benjamin Wright <benwright@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#27497}
> 
> TBR=brandtr@webrtc.org,steveanton@webrtc.org,solenberg@webrtc.org,ossu@webrtc.org,stefan@webrtc.org,benwright@webrtc.org
> 
> Change-Id: Ia9ec70263762c34671af13f0d519e636eb8473cd
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: webrtc:10512
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132013
> Reviewed-by: Henrik Boström <hbos@webrtc.org>
> Commit-Queue: Henrik Boström <hbos@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27510}

TBR=brandtr@webrtc.org,steveanton@webrtc.org,solenberg@webrtc.org,hbos@webrtc.org,ossu@webrtc.org,stefan@webrtc.org,benwright@webrtc.org

Change-Id: I8e4b7965cf1d1a1554c3b46e6245f5ad0d2dcbb4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:10512
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131982
Reviewed-by: Benjamin Wright <benwright@webrtc.org>
Commit-Queue: Benjamin Wright <benwright@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27529}
diff --git a/api/crypto/frame_decryptor_interface.h b/api/crypto/frame_decryptor_interface.h
index 69f1375..ec900ab 100644
--- a/api/crypto/frame_decryptor_interface.h
+++ b/api/crypto/frame_decryptor_interface.h
@@ -34,8 +34,9 @@
   // returned when attempting to decrypt a frame. kRecoverable indicates that
   // there was an error with the given frame and so it should not be passed to
   // the decoder, however it hints that the receive stream is still decryptable
-  // which is important for determining when to send key frame requests.
-  enum class Status { kOk, kRecoverable, kFailedToDecrypt };
+  // which is important for determining when to send key frame requests
+  // kUnknown should never be returned by the implementor.
+  enum class Status { kOk, kRecoverable, kFailedToDecrypt, kUnknown };
 
   struct Result {
     Result(Status status, size_t bytes_written)
@@ -54,33 +55,15 @@
   // that the frames are in order if SRTP is enabled. The stream is not provided
   // here and it is up to the implementor to transport this information to the
   // receiver if they care about it. You must set bytes_written to how many
-  // bytes you wrote to in the frame buffer. 0 must be returned if successful
-  // all other numbers can be selected by the implementer to represent error
-  // codes.
-  // TODO(bugs.webrtc.org/10512) - Remove this after implementation rewrite.
-  virtual int Decrypt(cricket::MediaType media_type,
-                      const std::vector<uint32_t>& csrcs,
-                      rtc::ArrayView<const uint8_t> additional_data,
-                      rtc::ArrayView<const uint8_t> encrypted_frame,
-                      rtc::ArrayView<uint8_t> frame,
-                      size_t* bytes_written) {
-    bytes_written = 0;
-    return 1;
-  }
-
-  // TODO(bugs.webrtc.org/10512) - Remove the other decrypt function and turn
-  // this to a pure virtual.
+  // bytes you wrote to in the frame buffer. kOk must be returned if successful,
+  // kRecoverable should be returned if the failure was due to something other
+  // than a decryption failure. kFailedToDecrypt should be returned in all other
+  // cases.
   virtual Result Decrypt(cricket::MediaType media_type,
                          const std::vector<uint32_t>& csrcs,
                          rtc::ArrayView<const uint8_t> additional_data,
                          rtc::ArrayView<const uint8_t> encrypted_frame,
-                         rtc::ArrayView<uint8_t> frame) {
-    size_t bytes_written = 0;
-    const int status = Decrypt(media_type, csrcs, additional_data,
-                               encrypted_frame, frame, &bytes_written);
-    return Result(status == 0 ? Status::kOk : Status::kFailedToDecrypt,
-                  bytes_written);
-  }
+                         rtc::ArrayView<uint8_t> frame) = 0;
 
   // Returns the total required length in bytes for the output of the
   // decryption. This can be larger than the actual number of bytes you need but
diff --git a/api/test/fake_frame_decryptor.cc b/api/test/fake_frame_decryptor.cc
index b77017f..4af42a6 100644
--- a/api/test/fake_frame_decryptor.cc
+++ b/api/test/fake_frame_decryptor.cc
@@ -18,14 +18,14 @@
                                        uint8_t expected_postfix_byte)
     : fake_key_(fake_key), expected_postfix_byte_(expected_postfix_byte) {}
 
-int FakeFrameDecryptor::Decrypt(cricket::MediaType media_type,
-                                const std::vector<uint32_t>& csrcs,
-                                rtc::ArrayView<const uint8_t> additional_data,
-                                rtc::ArrayView<const uint8_t> encrypted_frame,
-                                rtc::ArrayView<uint8_t> frame,
-                                size_t* bytes_written) {
+FakeFrameDecryptor::Result FakeFrameDecryptor::Decrypt(
+    cricket::MediaType media_type,
+    const std::vector<uint32_t>& csrcs,
+    rtc::ArrayView<const uint8_t> additional_data,
+    rtc::ArrayView<const uint8_t> encrypted_frame,
+    rtc::ArrayView<uint8_t> frame) {
   if (fail_decryption_) {
-    return static_cast<int>(FakeDecryptStatus::FORCED_FAILURE);
+    return Result(Status::kFailedToDecrypt, 0);
   }
 
   RTC_CHECK_EQ(frame.size() + 1, encrypted_frame.size());
@@ -34,11 +34,10 @@
   }
 
   if (encrypted_frame[frame.size()] != expected_postfix_byte_) {
-    return static_cast<int>(FakeDecryptStatus::INVALID_POSTFIX);
+    return Result(Status::kFailedToDecrypt, 0);
   }
 
-  *bytes_written = frame.size();
-  return static_cast<int>(FakeDecryptStatus::OK);
+  return Result(Status::kOk, frame.size());
 }
 
 size_t FakeFrameDecryptor::GetMaxPlaintextByteSize(
diff --git a/api/test/fake_frame_decryptor.h b/api/test/fake_frame_decryptor.h
index cb370b9..05813db 100644
--- a/api/test/fake_frame_decryptor.h
+++ b/api/test/fake_frame_decryptor.h
@@ -35,12 +35,11 @@
                               uint8_t expected_postfix_byte = 255);
   // Fake decryption that just xors the payload with the 1 byte key and checks
   // the postfix byte. This will always fail if fail_decryption_ is set to true.
-  int Decrypt(cricket::MediaType media_type,
-              const std::vector<uint32_t>& csrcs,
-              rtc::ArrayView<const uint8_t> additional_data,
-              rtc::ArrayView<const uint8_t> encrypted_frame,
-              rtc::ArrayView<uint8_t> frame,
-              size_t* bytes_written) override;
+  Result Decrypt(cricket::MediaType media_type,
+                 const std::vector<uint32_t>& csrcs,
+                 rtc::ArrayView<const uint8_t> additional_data,
+                 rtc::ArrayView<const uint8_t> encrypted_frame,
+                 rtc::ArrayView<uint8_t> frame) override;
   // Always returns 1 less than the size of the encrypted frame.
   size_t GetMaxPlaintextByteSize(cricket::MediaType media_type,
                                  size_t encrypted_frame_size) override;
diff --git a/api/test/mock_frame_decryptor.h b/api/test/mock_frame_decryptor.h
index feac9b3..77aa4f9 100644
--- a/api/test/mock_frame_decryptor.h
+++ b/api/test/mock_frame_decryptor.h
@@ -23,13 +23,12 @@
   MockFrameDecryptor();
   ~MockFrameDecryptor() override;
 
-  MOCK_METHOD6(Decrypt,
-               int(cricket::MediaType,
-                   const std::vector<uint32_t>&,
-                   rtc::ArrayView<const uint8_t>,
-                   rtc::ArrayView<const uint8_t>,
-                   rtc::ArrayView<uint8_t>,
-                   size_t*));
+  MOCK_METHOD5(Decrypt,
+               Result(cricket::MediaType,
+                      const std::vector<uint32_t>&,
+                      rtc::ArrayView<const uint8_t>,
+                      rtc::ArrayView<const uint8_t>,
+                      rtc::ArrayView<uint8_t>));
 
   MOCK_METHOD2(GetMaxPlaintextByteSize,
                size_t(cricket::MediaType, size_t encrypted_frame_size));