MailboxToSurfaceBridge: produce texture exactly when we create mailbox

This refactors MailboxToSurfaceBridge a bit based on existing callers.
A follow-up change will merge GenMailboxCHROMIUM and
ProduceTextureDirectCHROMIUM.

DestroyMailboxTexture was dead code, so removed. We can resurrect in a
later CL if needed.

Bug: 847674
Change-Id: I8fa52a4b7288955d3571c41bdf7b23f0ca4290f0
Reviewed-on: https://chromium-review.googlesource.com/1083333Reviewed-by: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565114}

chrome/browser/android/vr/arcore_device/ar_image_transport.cc

@@ -148,14 +148,10 @@ void ARImageTransport::SetupHardwareBuffers() {
     std::unique_ptr<SharedFrameBuffer> buffer =
         std::make_unique<SharedFrameBuffer>();
     // Remote resources
-    std::unique_ptr<gpu::MailboxHolder> holder =
-        std::make_unique<gpu::MailboxHolder>();
-    mailbox_bridge_->GenerateMailbox(holder->mailbox);
-    holder->texture_target = GL_TEXTURE_2D;
-    buffer->mailbox_holder = std::move(holder);
-
+    buffer->mailbox_holder = std::make_unique<gpu::MailboxHolder>();
+    buffer->mailbox_holder->texture_target = GL_TEXTURE_2D;
     buffer->remote_texture_id =
-        mailbox_bridge_->CreateMailboxTexture(buffer->mailbox_holder->mailbox);
+        mailbox_bridge_->CreateMailboxTexture(&buffer->mailbox_holder->mailbox);
 
     // Local resources
     glGenTextures(1, &buffer->local_texture_id);

chrome/browser/android/vr/mailbox_to_surface_bridge.cc

@@ -353,14 +353,7 @@ void MailboxToSurfaceBridge::CreateGpuFence(
   gl_->DestroyGpuFenceCHROMIUM(id);
 }
 
-void MailboxToSurfaceBridge::GenerateMailbox(gpu::Mailbox& out_mailbox) {
-  TRACE_EVENT0("gpu", __FUNCTION__);
-  DCHECK(IsConnected());
-  gl_->GenMailboxCHROMIUM(out_mailbox.name);
-}
-
-uint32_t MailboxToSurfaceBridge::CreateMailboxTexture(
-    const gpu::Mailbox& mailbox) {
+uint32_t MailboxToSurfaceBridge::CreateMailboxTexture(gpu::Mailbox* mailbox) {
   TRACE_EVENT0("gpu", __FUNCTION__);
   DCHECK(IsConnected());
 
@@ -368,23 +361,12 @@ uint32_t MailboxToSurfaceBridge::CreateMailboxTexture(
   gl_->GenTextures(1, &tex);
   gl_->BindTexture(GL_TEXTURE_2D, tex);
 
-  gl_->ProduceTextureDirectCHROMIUM(tex, mailbox.name);
+  gl_->GenMailboxCHROMIUM(mailbox->name);
+  gl_->ProduceTextureDirectCHROMIUM(tex, mailbox->name);
 
   return tex;
 }
 
-void MailboxToSurfaceBridge::DestroyMailboxTexture(const gpu::Mailbox& mailbox,
-                                                   uint32_t texture_id) {
-  TRACE_EVENT0("gpu", __FUNCTION__);
-  DCHECK(IsConnected());
-
-  // Associating with texture ID 0 unbinds the previous binding without
-  // creating a new one.
-  gl_->ProduceTextureDirectCHROMIUM(0, mailbox.name);
-  GLuint tex = texture_id;
-  gl_->DeleteTextures(1, &tex);
-}
-
 uint32_t MailboxToSurfaceBridge::BindSharedBufferImage(
     gfx::GpuMemoryBuffer* buffer,
     const gfx::Size& size,

chrome/browser/android/vr/mailbox_to_surface_bridge.h

@@ -112,15 +112,10 @@ class MailboxToSurfaceBridge {
       const gpu::SyncToken& sync_token,
       base::OnceCallback<void(std::unique_ptr<gfx::GpuFence>)> callback);
 
-  void GenerateMailbox(gpu::Mailbox& out_mailbox);
-
-  // Creates a texture and binds it to the mailbox. Returns its
-  // texture ID in the command buffer context. (Don't use that
+  // Creates a texture and binds it to a newly created mailbox. Returns its
+  // mailbox and texture ID in the command buffer context. (Don't use that
   // in the local GL context, it's not valid there.)
-  uint32_t CreateMailboxTexture(const gpu::Mailbox& mailbox);
-
-  // Unbinds the texture from the mailbox and destroys it.
-  void DestroyMailboxTexture(const gpu::Mailbox& mailbox, uint32_t texture_id);
+  uint32_t CreateMailboxTexture(gpu::Mailbox* mailbox);
 
   // Creates a GLImage from the |buffer| and binds it to the supplied texture_id
   // in the GPU process. Returns the image ID in the command buffer context.

chrome/browser/android/vr/vr_shell_gl.cc

@@ -615,13 +615,10 @@ void VrShellGl::WebVrPrepareSharedBuffer(const gfx::Size& size) {
     buffer = webxr_->GetAnimatingFrame()->shared_buffer.get();
 
     // Remote resources
-    auto holder = std::make_unique<gpu::MailboxHolder>();
-    DCHECK(holder);
-    mailbox_bridge_->GenerateMailbox(holder->mailbox);
-    holder->texture_target = GL_TEXTURE_2D;
+    buffer->mailbox_holder = std::make_unique<gpu::MailboxHolder>();
+    buffer->mailbox_holder->texture_target = GL_TEXTURE_2D;
     buffer->remote_texture =
-        mailbox_bridge_->CreateMailboxTexture(holder->mailbox);
-    buffer->mailbox_holder = std::move(holder);
+        mailbox_bridge_->CreateMailboxTexture(&buffer->mailbox_holder->mailbox);
 
     // Local resources
     glGenTextures(1, &buffer->local_texture);