CopyOutputResult must have a working release callback when received over mojo

cc/ipc/copy_output_result_struct_traits.cc

Index: cc/ipc/copy_output_result_struct_traits.cc
diff --git a/cc/ipc/copy_output_result_struct_traits.cc b/cc/ipc/copy_output_result_struct_traits.cc
index 0398fe115cd52463b56fbf2a1a1540d3d96b2935..5f9845e6af214ab1b81eab7dea4e275360f599b3 100644
--- a/cc/ipc/copy_output_result_struct_traits.cc
+++ b/cc/ipc/copy_output_result_struct_traits.cc
@@ -4,9 +4,78 @@
 
 #include "cc/ipc/copy_output_result_struct_traits.h"
 
+#include "mojo/public/cpp/bindings/strong_binding.h"
+
+namespace {
+
+// This class retains the release_callback_ of the CopyOutputResult that is
+// being sent over mojo. A TextureMailboxReleaserPtr that talks to this impl
+// object will be sent over mojo instead of the release_callback_ (which is not
+// serializable). Once the client calls Release, the release_callback_ will be
+// called. An object of this class will remain alive until the MessagePipe
+// attached to it goes away (i.e. StrongBinding is used).
+class TextureMailboxReleaserImpl : public cc::mojom::TextureMailboxReleaser {
+ public:
+  TextureMailboxReleaserImpl(
+      std::unique_ptr<cc::SingleReleaseCallback> release_callback)
+      : release_callback_(std::move(release_callback)) {
+    DCHECK(release_callback_);
+  }
+
+  ~TextureMailboxReleaserImpl() override {
+    // If the client fails to call Release, we should do it ourselves because
+    // release_callback_ will fail if it's never called.
+    if (release_callback_)
+      release_callback_->Run(gpu::SyncToken(), true);
+  }
+
+  // mojom::TextureMailboxReleaser implementation:
+  void Release(const gpu::SyncToken& sync_token, bool is_lost) override {
+    if (!release_callback_)
+      return;
+    release_callback_->Run(sync_token, is_lost);
+    release_callback_.reset();
+  }
+
+ private:
+  std::unique_ptr<cc::SingleReleaseCallback> release_callback_;
+};
+
+void Release(cc::mojom::TextureMailboxReleaserPtr ptr,
+             const gpu::SyncToken& sync_token,
+             bool is_lost) {
+  ptr->Release(sync_token, is_lost);
+}
+
+}  // namespace
+
 namespace mojo {
 
 // static
+const SkBitmap& StructTraits<cc::mojom::CopyOutputResultDataView,
+                             std::unique_ptr<cc::CopyOutputResult>>::
+    bitmap(const std::unique_ptr<cc::CopyOutputResult>& result) {
+  static SkBitmap* null_bitmap = new SkBitmap();
+  if (!result->bitmap_)
+    return *null_bitmap;
+  return *result->bitmap_;
+}
+
+// static
+cc::mojom::TextureMailboxReleaserPtr
+StructTraits<cc::mojom::CopyOutputResultDataView,
+             std::unique_ptr<cc::CopyOutputResult>>::
+    releaser(const std::unique_ptr<cc::CopyOutputResult>& result) {
+  if (!result->release_callback_)
+    return {};
+  cc::mojom::TextureMailboxReleaserPtr releaser;
+  auto impl = base::MakeUnique<TextureMailboxReleaserImpl>(
+      std::move(result->release_callback_));
+  MakeStrongBinding(std::move(impl), MakeRequest(&releaser));
+  return releaser;
+}
+
+// static
 bool StructTraits<cc::mojom::CopyOutputResultDataView,
                   std::unique_ptr<cc::CopyOutputResult>>::
     Read(cc::mojom::CopyOutputResultDataView data,
@@ -23,19 +92,26 @@ bool StructTraits<cc::mojom::CopyOutputResultDataView,
   if (!data.ReadTextureMailbox(&result->texture_mailbox_))
     return false;
 
+  auto releaser = data.TakeReleaser<cc::mojom::TextureMailboxReleaserPtr>();
+  if (releaser) {
+    // CopyOutputResult does not have a TextureMailboxReleaserPtr member.
+    // We use base::Bind to turn TextureMailboxReleaser::Release into a
+    // ReleaseCallback.
+    result->release_callback_ = cc::SingleReleaseCallback::Create(
+        base::Bind(Release, base::Passed(&releaser)));
+  }
+
+  // Check that release callback and texture mailbox are set together.
+  if (!!result->release_callback_ != result->texture_mailbox_.IsValid())
+    return false;
+
+  // We can't have both a bitmap and a texture at the same time.
+  if (result->HasBitmap() && result->HasTexture())
+    return false;
+
   *out_p = std::move(result);
 
   return true;
 }
 
-// static
-const SkBitmap& StructTraits<cc::mojom::CopyOutputResultDataView,
-                             std::unique_ptr<cc::CopyOutputResult>>::
-    bitmap(const std::unique_ptr<cc::CopyOutputResult>& result) {
-  static SkBitmap* null_bitmap = new SkBitmap();
-  if (!result->bitmap_)
-    return *null_bitmap;
-  return *result->bitmap_;
-}
-
 }  // namespace mojo