Make GPU back-pressure work with remote CALayers

content/common/gpu/image_transport_surface_iosurface_mac.cc

 // Copyright 2014 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.
 
 #include "content/common/gpu/image_transport_surface_iosurface_mac.h"
 
 #include "content/common/gpu/gpu_messages.h"
 #include "content/common/gpu/surface_handle_types_mac.h"
 
 namespace content {
@@ skipping 22 matching lines @@
 void AddIntegerValue(CFMutableDictionaryRef dictionary,
                      const CFStringRef key,
                      int32 value) {
   base::ScopedCFTypeRef<CFNumberRef> number(
       CFNumberCreate(NULL, kCFNumberSInt32Type, &value));
   CFDictionaryAddValue(dictionary, key, number.get());
 }
 
 }  // namespace
 
-IOSurfaceStorageProvider::IOSurfaceStorageProvider() {}
+IOSurfaceStorageProvider::IOSurfaceStorageProvider(
+    ImageTransportSurfaceFBO* transport_surface)
+        : transport_surface_(transport_surface) {}
 
 IOSurfaceStorageProvider::~IOSurfaceStorageProvider() {
   DCHECK(!io_surface_);
 }
 
 gfx::Size IOSurfaceStorageProvider::GetRoundedSize(gfx::Size size) {
   return gfx::Size(RoundUpSurfaceDimension(size.width()),
                    RoundUpSurfaceDimension(size.height()));
 }
 
@@ skipping 47 matching lines @@
 void IOSurfaceStorageProvider::FreeColorBufferStorage() {
   io_surface_.reset();
   io_surface_id_ = 0;
 }
 
 uint64 IOSurfaceStorageProvider::GetSurfaceHandle() const {
   return SurfaceHandleFromIOSurfaceID(io_surface_id_);
 }
 
 void IOSurfaceStorageProvider::WillSwapBuffers() {
+  // The browser compositor will throttle itself, so we are free to unblock the
+  // context immediately. Make sure that the browser is doing its throttling
+  // appropriately by ensuring that the previous swap was acknowledged before
+  // we get another swap.
+  DCHECK(pending_swapped_surfaces_.empty());
+  pending_swapped_surfaces_.push_back(io_surface_);
+  transport_surface_->UnblockContextAfterPendingSwap();
+}
+
+void IOSurfaceStorageProvider::CanFreeSwappedBuffer() {
+  DCHECK(!pending_swapped_surfaces_.empty());
+  pending_swapped_surfaces_.pop_front();
 }
 
 }  //  namespace content