Draw the offscreen texture to reflector's surface without extra copy

content/browser/compositor/gpu_browser_compositor_output_surface.cc

Index: content/browser/compositor/gpu_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/gpu_browser_compositor_output_surface.cc b/content/browser/compositor/gpu_browser_compositor_output_surface.cc
index 114a84f33b4195425bff6edfa041af21c5e07876..ee666790bfb5f4e76bbf87f3781940e5f00b2f53 100644
--- a/content/browser/compositor/gpu_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/gpu_browser_compositor_output_surface.cc
@@ -7,9 +7,11 @@
 #include "cc/output/compositor_frame.h"
 #include "cc/output/output_surface_client.h"
 #include "content/browser/compositor/browser_compositor_overlay_candidate_validator.h"
+#include "content/browser/compositor/owned_mailbox.h"
 #include "content/browser/compositor/reflector_impl.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/common/gpu/client/context_provider_command_buffer.h"
+#include "content/common/gpu/client/gl_helper.h"
 #include "content/public/browser/browser_thread.h"
 #include "gpu/command_buffer/client/context_support.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
@@ -32,10 +34,14 @@ GpuBrowserCompositorOutputSurface::GpuBrowserCompositorOutputSurface(
                      base::Unretained(this))),
       update_vsync_parameters_callback_(base::Bind(
           &BrowserCompositorOutputSurface::OnUpdateVSyncParametersFromGpu,
-          base::Unretained(this))) {
+          base::Unretained(this))),
+      mirrored_compositor_gl_helper_texture_id_(0) {
 }
 
-GpuBrowserCompositorOutputSurface::~GpuBrowserCompositorOutputSurface() {}
+GpuBrowserCompositorOutputSurface::~GpuBrowserCompositorOutputSurface() {
+  DCHECK(!reflector_);
+  DeleteTexture();
+}
 
 CommandBufferProxyImpl*
 GpuBrowserCompositorOutputSurface::GetCommandBufferProxy() {
@@ -60,6 +66,37 @@ bool GpuBrowserCompositorOutputSurface::BindToClient(
   return true;
 }
 
+void GpuBrowserCompositorOutputSurface::DeleteTexture() {
+  if (mirrored_compositor_gl_helper_.get()) {
+    mirrored_compositor_gl_helper_->DeleteTexture(
+        mirrored_compositor_gl_helper_texture_id_);
+    mailbox_ = nullptr;
+    mirrored_compositor_gl_helper_texture_id_ = 0;
+    mirrored_compositor_gl_helper_ = nullptr;
+  }
+}
+
+void GpuBrowserCompositorOutputSurface::OnReflectorChanged() {
+  if (!reflector_) {
+    DeleteTexture();
+  } else {
+    GLHelper* shared_helper =
+        ImageTransportFactory::GetInstance()->GetGLHelper();
+    mailbox_ = new OwnedMailbox(shared_helper);
+
+    // Create a GLHelper attached to the mirrored compositor's output
+    // surface for copying the output of the mirrored compositor.
+    mirrored_compositor_gl_helper_.reset(new GLHelper(
+        context_provider()->ContextGL(), context_provider()->ContextSupport()));
+    // Create a texture id in the name space of the new GLHelper to update the
+    // mailbox being held by the |mirroring_layer_|.

[piman, 2015/05/13 19:46:23]

can you add a DCHECK(!mirrored_compositor_gl_helper_texture_id_)?

I'm assuming we only transition from !reflector_ to !!reflector_ and vice versa.
Otherwise we leak the texture.

[oshima, 2015/05/14 14:44:58]

Done.

+    mirrored_compositor_gl_helper_texture_id_ =
+        mirrored_compositor_gl_helper_->ConsumeMailboxToTexture(
+            mailbox_->mailbox(), mailbox_->sync_point());
+    reflector_->OnSourceTextureMailboxUpdated(mailbox_);
+  }
+}
+
 void GpuBrowserCompositorOutputSurface::SwapBuffers(
     cc::CompositorFrame* frame) {
   DCHECK(frame->gl_frame_data);
@@ -68,10 +105,28 @@ void GpuBrowserCompositorOutputSurface::SwapBuffers(
 
   if (reflector_) {
     if (frame->gl_frame_data->sub_buffer_rect ==
-        gfx::Rect(frame->gl_frame_data->size))
+        gfx::Rect(frame->gl_frame_data->size)) {
+      gfx::Size size = SurfaceSize();
+      mirrored_compositor_gl_helper_->CopyTextureFullImage(
+          mirrored_compositor_gl_helper_texture_id_, size);
+      // Insert a barrier to make the copy show up in the mirroring compositor's
+      // mailbox. Since the the compositor contexts and the
+      // ImageTransportFactory's
+      // GLHelper are all on the same GPU channel, this is sufficient instead of
+      // plumbing through a sync point.
+      mirrored_compositor_gl_helper_->InsertOrderingBarrier();
+
       reflector_->OnSourceSwapBuffers();
-    else
-      reflector_->OnSourcePostSubBuffer(frame->gl_frame_data->sub_buffer_rect);
+    } else {
+      const gfx::Rect& rect = frame->gl_frame_data->sub_buffer_rect;
+
+      mirrored_compositor_gl_helper_->CopyTextureSubImage(
+          mirrored_compositor_gl_helper_texture_id_, rect);
+      // Insert a barrier for the same reason above.
+      mirrored_compositor_gl_helper_->InsertOrderingBarrier();
+
+      reflector_->OnSourcePostSubBuffer(rect);
+    }
   }
 
   if (frame->gl_frame_data->sub_buffer_rect ==