cc: Release pending overlay resources on swap-ack.

cc/output/gl_renderer.cc

 // Copyright 2010 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 "cc/output/gl_renderer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 2747 matching lines @@
       swapping_overlay_resources_.size() > 2) {
     swapping_overlay_resources_.pop_front();
   }
 
   output_surface_->SwapBuffers(std::move(compositor_frame));
 
   swap_buffer_rect_ = gfx::Rect();
 }
 
 void GLRenderer::SwapBuffersComplete() {
-  // Once a resouce has been swap-ACKed, send a query to the GPU process to ask
-  // if the resource is no longer being consumed by the system compositor. The
-  // response will come with the next swap-ACK.
   if (settings_->release_overlay_resources_after_gpu_query) {
+    // Once a resource has been swap-ACKed, send a query to the GPU process to
+    // ask if the resource is no longer being consumed by the system compositor.
+    // The response will come with the next swap-ACK.
     if (!swapping_overlay_resources_.empty()) {
       for (OverlayResourceLock& lock : swapping_overlay_resources_.front()) {
         unsigned texture = lock->texture_id();
         if (swapped_and_acked_overlay_resources_.find(texture) ==
             swapped_and_acked_overlay_resources_.end()) {
           swapped_and_acked_overlay_resources_[texture] = std::move(lock);
         }
       }
       swapping_overlay_resources_.pop_front();
     }
 
     if (!swapped_and_acked_overlay_resources_.empty()) {
       std::vector<unsigned> textures;
       textures.reserve(swapped_and_acked_overlay_resources_.size());
       for (auto& pair : swapped_and_acked_overlay_resources_) {
         textures.push_back(pair.first);
       }
       gl_->ScheduleCALayerInUseQueryCHROMIUM(textures.size(), textures.data());
     }
+  } else if (swapping_overlay_resources_.size() > 1) {
+    // If a query is not needed to release the overlay buffers, we can
+    // assume that once a swap buffer is completed only the last set of
+    // submitted overlay buffers are still in use by GL/Hardware Display.
+    DCHECK_EQ(2u, swapping_overlay_resources_.size());
+    swapping_overlay_resources_.pop_front();
   }
 }
 
 void GLRenderer::DidReceiveTextureInUseResponses(
     const gpu::TextureInUseResponses& responses) {
   DCHECK(settings_->release_overlay_resources_after_gpu_query);
   for (const gpu::TextureInUseResponse& response : responses) {
     if (!response.in_use) {
       swapped_and_acked_overlay_resources_.erase(response.texture);
     }
@@ skipping 889 matching lines @@
       texture_id = pending_overlay_resources_.back()->texture_id();
     }
 
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order, overlay.transform, texture_id,
         ToNearestRect(overlay.display_rect), overlay.uv_rect);
   }
 }
 
 }  // namespace cc