Add logic to ResourceProvider to correctly lock GpuMemoryBuffer Resources.

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 1c33fe663f15adfcab6193ea2b8b2809165fce21..6579f2c2424b26462f0fe18025e6bf73867fce52 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -395,6 +395,8 @@ GLRenderer::~GLRenderer() {
   }
 
   swapped_overlay_resources_.clear();
+  ReleaseGpuMemoryBufferResources();
+
   CleanupSharedObjects();
 }
 
@@ -2727,6 +2729,16 @@ void GLRenderer::SwapBuffers(const CompositorFrameMetadata& metadata) {
       swapped_overlay_resources_.size() > 2) {
     swapped_overlay_resources_.pop_front();
   }
+
+  // Make the assumption that by the time a second SwapBuffers has come in, the
+  // resources in |pending_gmb_resources_| have been received, processed, (and
+  // possibly displayed) by the Window Server.
+  if (!pending_gmb_resources_.empty()) {
+    in_use_gmb_resources_.push_back(std::move(pending_gmb_resources_));
+    pending_gmb_resources_.clear();
+  }
+  ReleaseGpuMemoryBufferResources();
+
   swap_buffer_rect_ = gfx::Rect();
 }
 
@@ -3603,10 +3615,10 @@ void GLRenderer::ScheduleCALayers(DrawingFrame* frame) {
   for (const CALayerOverlay& ca_layer_overlay : frame->ca_layer_overlay_list) {
     unsigned texture_id = 0;
     if (ca_layer_overlay.contents_resource_id) {
-      pending_overlay_resources_.push_back(
-          base::WrapUnique(new ResourceProvider::ScopedReadLockGL(
+      pending_gmb_resources_.push_back(
+          base::WrapUnique(new ResourceProvider::ScopedReadLockGpuMemoryBuffer(
               resource_provider_, ca_layer_overlay.contents_resource_id)));
-      texture_id = pending_overlay_resources_.back()->texture_id();
+      texture_id = pending_gmb_resources_.back()->texture_id();
     }
     GLfloat contents_rect[4] = {
         ca_layer_overlay.contents_rect.x(), ca_layer_overlay.contents_rect.y(),
@@ -3658,4 +3670,22 @@ void GLRenderer::ScheduleOverlays(DrawingFrame* frame) {
   }
 }
 
+void GLRenderer::ReleaseGpuMemoryBufferResources() {
+  // Remove resources that are no longer in use by the Window Server.
+  for (auto& resources_vector : in_use_gmb_resources_) {
+    resources_vector.erase(
+        std::remove_if(
+            resources_vector.begin(), resources_vector.end(),
+            [](std::unique_ptr<ResourceProvider::ScopedReadLockGpuMemoryBuffer>&
+                   lock) { return !lock->IsInUseByMacOSWindowServer(); }),
+        resources_vector.end());
+  }
+
+  // Remove vectors that are empty.
+  in_use_gmb_resources_.erase(
+      std::remove_if(in_use_gmb_resources_.begin(), in_use_gmb_resources_.end(),
+                     [](GmbResourceLockList& list) { return list.empty(); }),
+      in_use_gmb_resources_.end());
+}
+
 }  // namespace cc