Refactor client visibility handling

cc/output/context_cache_controller.cc

+// Copyright (c) 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.
+
+#include "cc/output/context_cache_controller.h"
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "gpu/command_buffer/client/context_support.h"
+#include "third_party/skia/include/gpu/GrContext.h"
+
+namespace cc {
+ContextCacheController::ScopedVisibility::ScopedVisibility() = default;
+
+ContextCacheController::ScopedVisibility::~ScopedVisibility() {
+  DCHECK(released_);
+}
+
+void ContextCacheController::ScopedVisibility::Release() {
+  DCHECK(!released_);
+  released_ = true;
+}
+
+ContextCacheController::ContextCacheController(
+    gpu::ContextSupport* context_support)
+    : context_support_(context_support) {}
+
+void ContextCacheController::SetGrContext(GrContext* gr_context) {
+  gr_context_ = gr_context;
+}
+
+std::unique_ptr<ContextCacheController::ScopedVisibility>
+ContextCacheController::ClientBecameVisible() {
+  bool became_visible = num_clients_visible_ == 0;
+  ++num_clients_visible_;
+
+  if (became_visible)
+    context_support_->SetAggressivelyFreeResources(false);
+
+  return base::WrapUnique(new ScopedVisibility());
+}
+
+void ContextCacheController::ClientBecameNotVisible(
+    std::unique_ptr<ScopedVisibility> scoped_visibility) {
+  DCHECK(scoped_visibility);
+  scoped_visibility->Release();
+
+  DCHECK_GT(num_clients_visible_, 0u);
+  --num_clients_visible_;
+
+  if (num_clients_visible_ == 0) {
+    if (gr_context_)
+      gr_context_->freeGpuResources();
+    context_support_->SetAggressivelyFreeResources(true);
+  }
+}
+
+}  // namespace cc