[Chromecast] Change DecryptContext Decrypt API

1. Change |output| from vector<uint8_t> to uint8_t*.
2. Add param |data_offset|.

BUG=internal b/31219712
TEST=build cast_shell

Review-Url: https://codereview.chromium.org/2450563002
Cr-Commit-Position: refs/heads/master@{#427275}

chromecast/media/base/decrypt_context_impl.cc

@@ -31,12 +31,6 @@ CastKeySystem DecryptContextImpl::GetKeySystem() {
   return key_system_;
 }
 
-bool DecryptContextImpl::Decrypt(CastDecoderBuffer* buffer,
-                                 std::vector<uint8_t>* output) {
-  output->resize(buffer->data_size());
-  return Decrypt(buffer, output->data(), 0);
-}
-
 bool DecryptContextImpl::Decrypt(CastDecoderBuffer* buffer,
                                  uint8_t* output,
                                  size_t data_offset) {

chromecast/media/base/decrypt_context_impl.h

@@ -31,20 +31,8 @@ class DecryptContextImpl : public DecryptContext {
   // DecryptContext implementation:
   CastKeySystem GetKeySystem() override;
   bool Decrypt(CastDecoderBuffer* buffer,
-               std::vector<uint8_t>* output) final;
-
-  // TODO(smcgruer): Replace DecryptContext::Decrypt with this one in next
-  // public api releasing.
-  // Decrypts the given buffer. Returns true/false for success/failure.
-  //
-  // The decrypted data will be of size |buffer.data_size()| and there must be
-  // enough space in |output| to store that data.
-  //
-  // If non-zero, |data_offset| specifies an offset to be applied to |output|
-  // before the decrypted data is written.
-  virtual bool Decrypt(CastDecoderBuffer* buffer,
-                       uint8_t* output,
-                       size_t data_offset);
+               uint8_t* output,
+               size_t data_offset) override;
 
   // Similar as the above one. Decryption success or not will be returned in
   // |decrypt_cb|. |decrypt_cb| will be called on caller's thread.

chromecast/public/media/decrypt_context.h

@@ -22,10 +22,16 @@ class DecryptContext {
   // Get the key system to use for decryption.
   virtual CastKeySystem GetKeySystem() = 0;
 
-  // Decrypts the given buffer.  Returns true/false for success/failure,
-  // and places the decrypted data in output if successful.
+  // Decrypts the given buffer. Returns true/false for success/failure.
+  //
+  // The decrypted data will be of size |buffer.data_size()| and there must be
+  // enough space in |output| to store that data.
+  //
+  // If non-zero, |data_offset| specifies an offset to be applied to |output|
+  // before the decrypted data is written.
   virtual bool Decrypt(CastDecoderBuffer* buffer,
-                       std::vector<uint8_t>* output) = 0;
+                       uint8_t* output,
+                       size_t data_offset) = 0;
 };
 
 }  // namespace media