[Aura] Added Support for rendering software compositor frames as cc::TextureLayers.

ui/aura/window.cc

Index: ui/aura/window.cc
diff --git a/ui/aura/window.cc b/ui/aura/window.cc
index 5160bf6c34fbd23f33c5f943d2a8fa9b325b5ba3..79fb08335af443bd9fad03fad266a7d883afbe86 100644
--- a/ui/aura/window.cc
+++ b/ui/aura/window.cc
@@ -34,6 +34,15 @@
 
 namespace aura {
 
+namespace {
+
+void MailboxReleaseCallback(base::SharedMemory* shared_memory,
+                            unsigned sync_point, bool lost_resource) {
+  delete shared_memory;
+}
+
+}  // namespace
+
 Window::Window(WindowDelegate* delegate)
     : type_(client::WINDOW_TYPE_UNKNOWN),
       owned_by_parent_(true),
@@ -145,6 +154,9 @@ ui::Layer* Window::RecreateLayer() {
     return NULL;
 
   old_layer->set_delegate(NULL);
+  float mailbox_scale_factor;
+  cc::TextureMailbox old_mailbox =
+      old_layer->GetTextureMailbox(&mailbox_scale_factor);
   scoped_refptr<ui::Texture> old_texture = old_layer->external_texture();
   if (delegate_ && old_texture)
     old_layer->SetExternalTexture(delegate_->CopyTexture());
@@ -160,6 +172,27 @@ ui::Layer* Window::RecreateLayer() {
   // crbug.com/175211.
   if (delegate_ && old_texture)
     layer_->SetExternalTexture(old_texture);
+  else if (old_mailbox.IsValid()) {

[piman, 2013/06/05 00:30:55]

nit: both sides of the else should have brackets if one side has them.

[slavi, 2013/06/06 23:02:47]

Done.

+    DCHECK(old_mailbox.IsSharedMemory());
+
+    const size_t size = old_mailbox.shared_memory_size_in_bytes();
+    scoped_ptr<base::SharedMemory> new_buffer(new base::SharedMemory);
+    new_buffer->CreateAndMapAnonymous(size);
+
+    const base::SharedMemoryHandle old_handle =
+        base::SharedMemory::DuplicateHandle(old_mailbox.handle());
+    base::SharedMemory old_buffer(old_handle, false);

[piman, 2013/06/05 00:30:55]

What if, instead of just the handle, we also passed the pointer into the
TextureMailbox: we could have the RWHVA Map the shm, and do the size check
(rather than deep inside the ResourceProvider), and we wouldn't have to
duplicate yet-once-more here, just to be able to access the data - it'd already
be mapped.
After all, the only reason we need the handle in the RP is to be able to send it
to the parent compositor, there's no fundamental reason to have the RP be the
one that maps.

[slavi, 2013/06/06 23:02:47]

Done.

+    old_buffer.Map(size);
+    if (old_buffer.memory() && new_buffer->memory()) {
+      memcpy(new_buffer->memory(), old_buffer.memory(), size);
+      cc::TextureMailbox::ReleaseCallback callback =
+          base::Bind(MailboxReleaseCallback, new_buffer.release());

[piman, 2013/06/05 00:30:55]

nit: you can use Passed(new_buffer), and make MailboxReleaseCallback take a
scoped_ptr and this makes it safer if ever the callback is destroyed without
being called because the message loop is gone or something.

[slavi, 2013/06/06 23:02:47]

Done.

+      cc::TextureMailbox new_mailbox(new_buffer->handle(),
+                                     old_mailbox.shared_memory_size(),
+                                     callback);
+      layer_->SetTextureMailbox(new_mailbox, mailbox_scale_factor);
+    }
+  }
 
   UpdateLayerName(name_);
   layer_->SetFillsBoundsOpaquely(!transparent_);
@@ -313,10 +346,6 @@ void Window::SchedulePaintInRect(const gfx::Rect& rect) {
   }
 }
 
-void Window::SetExternalTexture(ui::Texture* texture) {
-  layer_->SetExternalTexture(texture);
-}
-
 void Window::SetDefaultParentByRootWindow(RootWindow* root_window,
                                           const gfx::Rect& bounds_in_screen) {
   DCHECK(root_window);