Display Compositor: Allocate LocalFrameId in client.

cc/ipc/mojo_compositor_frame_sink.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module cc.mojom;
 
 import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/compositor_frame.mojom";
 import "cc/ipc/frame_sink_id.mojom";
+import "cc/ipc/local_frame_id.mojom";
 import "cc/ipc/returned_resource.mojom";
 
 // A MojoCompositorFrameSink is an interface for receiving CompositorFrame
 // structs. A CompositorFrame contains the complete output meant for display.
 // Each time a client has a graphical update, and receives an OnBeginFrame, it
 // is responsible for creating a CompositorFrame to update its portion of the
 // screen.
 interface MojoCompositorFrameSink {
   // Lets the display compositor know that the client wishes to receive the next
   // BeginFrame event.
   SetNeedsBeginFrame(bool needs_begin_frame);
 
   // Submits a CompositorFrame to the display compositor that will be presented
   // to screen the next time frames from all CompositorFrameSinks are aggregated
-  // to produce a display CompositorFrame.
+  // to produce a display CompositorFrame. If a client wishes to allocate a new
+  // surface (e.g. during resize), then it can simply allocate a new
+  // |local_frame_id|.
   // For successful swaps, the implementation must call
   // DidReceiveCompositorFrameAck() asynchronously when the frame has been
   // processed in order to unthrottle the next frame.
-  SubmitCompositorFrame(cc.mojom.CompositorFrame frame);
+  SubmitCompositorFrame(cc.mojom.LocalFrameId local_frame_id,
+                        cc.mojom.CompositorFrame frame);
 
   // TODO(fsamuel): ReadbackBitmap API would be useful here.
 };
 
 interface MojoCompositorFrameSinkClient {
   // Notification that the previous CompositorFrame given to
   // SubmitCompositorFrame() has been processed and that another frame
   // can be submitted. This provides backpressure from the display compositor
   // so that frames are submitted only at the rate it can handle them.
   // TODO(fsamuel): This method ought not be necessary with unified BeginFrame.
   // However, there's a fair amount of cleanup and refactoring necessary to get
   // rid of it.
   DidReceiveCompositorFrameAck();
 
   // Notification for the client to generate a CompositorFrame.
   OnBeginFrame(BeginFrameArgs args);
 
   // Returns resources sent to SubmitCompositorFrame to be reused or freed.
   ReclaimResources(ReturnedResourceArray resources);
 };
 
 // MojoCompositorFrameSinkPrivate is used by the display compositor host to set
 // up BeginFrameSource hierarchies.  This API lives in SurfaceManager but is
 // called from here in order to ensure that hierarchy registration does not race
 // CompositorFrameSink creation.
 interface MojoCompositorFrameSinkPrivate {
   AddChildFrameSink(FrameSinkId child_frame_sink_id);
   RemoveChildFrameSink(FrameSinkId child_frame_sink_id);
 };