[WIP] cc: Plumb SurfaceId from clients

content/renderer/gpu/compositor_output_surface.cc

Index: content/renderer/gpu/compositor_output_surface.cc
diff --git a/content/renderer/gpu/compositor_output_surface.cc b/content/renderer/gpu/compositor_output_surface.cc
index f341e25fbb002293ed6464c8911c4934f0b20400..7551a8cbff19274e7cab858c2cef679e81bb424b 100644
--- a/content/renderer/gpu/compositor_output_surface.cc
+++ b/content/renderer/gpu/compositor_output_surface.cc
@@ -23,6 +23,7 @@
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "gpu/ipc/client/command_buffer_proxy_impl.h"
 #include "ipc/ipc_sync_channel.h"
+#include "ui/gfx/geometry/dip_util.h"
 
 namespace content {
 
@@ -40,6 +41,8 @@ CompositorOutputSurface::CompositorOutputSurface(
           RenderThreadImpl::current()->compositor_message_filter()),
       message_sender_(RenderThreadImpl::current()->sync_message_filter()),
       frame_swap_message_queue_(swap_frame_message_queue),
+      allocator_(0),
+      current_scale_factor_(1.f),
       routing_id_(routing_id) {
   DCHECK(output_surface_filter_);
   DCHECK(frame_swap_message_queue_);
@@ -58,6 +61,8 @@ CompositorOutputSurface::CompositorOutputSurface(
           RenderThreadImpl::current()->compositor_message_filter()),
       message_sender_(RenderThreadImpl::current()->sync_message_filter()),
       frame_swap_message_queue_(swap_frame_message_queue),
+      allocator_(0),
+      current_scale_factor_(1.f),
       routing_id_(routing_id) {
   DCHECK(output_surface_filter_);
   DCHECK(frame_swap_message_queue_);
@@ -103,6 +108,20 @@ void CompositorOutputSurface::DetachFromClient() {
 }
 
 void CompositorOutputSurface::SwapBuffers(cc::CompositorFrame frame) {
+  cc::RenderPass* root_pass =
+      frame.delegated_frame_data->render_pass_list.back().get();
+  float frame_device_scale_factor = frame.metadata.device_scale_factor;
+  gfx::Size frame_size = root_pass->output_rect.size();
+  gfx::Size frame_size_in_dip =
+      gfx::ConvertSizeToDIP(frame_device_scale_factor, frame_size);
+  if (surface_id_.is_null() || frame_size != current_surface_size_ ||
+      frame_size_in_dip != current_surface_size_in_dip_) {
+    surface_id_ = allocator_.GenerateId();
+    current_surface_size_ = frame_size;
+    current_surface_size_in_dip_ = frame_size_in_dip;
+    current_scale_factor_ = frame_device_scale_factor;
+  }
+
   {
     std::unique_ptr<FrameSwapMessageQueue::SendMessageScope>
         send_message_scope =
@@ -113,7 +132,7 @@ void CompositorOutputSurface::SwapBuffers(cc::CompositorFrame frame) {
     FrameSwapMessageQueue::TransferMessages(&messages,
                                             &messages_to_deliver_with_frame);
     Send(new ViewHostMsg_SwapCompositorFrame(routing_id_, output_surface_id_,
-                                             frame,
+                                             surface_id_, frame,
                                              messages_to_deliver_with_frame));
     // ~send_message_scope.
   }