Mac: Don't repaint scrollbars every frame

cc/layers/painted_scrollbar_layer_unittest.cc

+// Copyright 2015 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/layers/painted_scrollbar_layer.h"
+
+#include "cc/layers/layer_settings.h"
+#include "cc/test/fake_layer_tree_host.h"
+#include "cc/test/fake_layer_tree_host_client.h"
+#include "cc/test/fake_scrollbar.h"
+#include "cc/test/test_task_graph_runner.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+using ::testing::Mock;
+using ::testing::_;
+
+namespace cc {
+
+namespace {
+
+class MockScrollbar : public FakeScrollbar {
+ public:
+  MockScrollbar() : FakeScrollbar(true, true, true) {}
+  MOCK_METHOD3(PaintPart,
+               void(SkCanvas* canvas,
+                    ScrollbarPart part,
+                    const gfx::Rect& content_rect));
+};
+
+TEST(PaintedScrollbarLayerTest, NeedsPaint) {
+  FakeLayerTreeHostClient fake_client_(FakeLayerTreeHostClient::DIRECT_3D);
+  TestTaskGraphRunner task_graph_runner_;
+  scoped_ptr<FakeLayerTreeHost> layer_tree_host_;
+  LayerSettings layer_settings_;
+
+  layer_tree_host_ =
+      FakeLayerTreeHost::Create(&fake_client_, &task_graph_runner_);
+  RendererCapabilities renderer_capabilities;
+  renderer_capabilities.max_texture_size = 2048;
+  layer_tree_host_->set_renderer_capabilities(renderer_capabilities);
+
+  MockScrollbar* scrollbar = new MockScrollbar();
+  scoped_refptr<PaintedScrollbarLayer> scrollbar_layer =
+      PaintedScrollbarLayer::Create(layer_settings_,
+                                    scoped_ptr<Scrollbar>(scrollbar).Pass(), 1);
+
+  scrollbar_layer->SetIsDrawable(true);
+  scrollbar_layer->SetBounds(gfx::Size(100, 100));
+
+  layer_tree_host_->SetRootLayer(scrollbar_layer);
+  EXPECT_EQ(scrollbar_layer->layer_tree_host(), layer_tree_host_.get());
+  scrollbar_layer->SavePaintProperties();
+
+  // Request no paint, but expect them to be painted because they have not
+  // yet bee initialized.

[enne (OOO), 2015/11/24 17:59:18]

typo

[ccameron, 2015/11/24 18:48:19]

Oops -- fixed.

+  scrollbar->set_needs_paint_thumb(false);
+  scrollbar->set_needs_paint_track(false);
+  EXPECT_CALL(*scrollbar, PaintPart(_, THUMB, _)).Times(1);
+  EXPECT_CALL(*scrollbar, PaintPart(_, TRACK, _)).Times(1);
+  scrollbar_layer->Update();
+  Mock::VerifyAndClearExpectations(scrollbar);
+
+  // The next update will paint nothing because the first update caused a paint.
+  EXPECT_CALL(*scrollbar, PaintPart(_, THUMB, _)).Times(0);
+  EXPECT_CALL(*scrollbar, PaintPart(_, TRACK, _)).Times(0);
+  scrollbar_layer->Update();
+  Mock::VerifyAndClearExpectations(scrollbar);
+
+  // Enable the thumb.
+  EXPECT_CALL(*scrollbar, PaintPart(_, THUMB, _)).Times(1);
+  EXPECT_CALL(*scrollbar, PaintPart(_, TRACK, _)).Times(0);
+  scrollbar->set_needs_paint_thumb(true);
+  scrollbar->set_needs_paint_track(false);
+  scrollbar_layer->Update();
+  Mock::VerifyAndClearExpectations(scrollbar);
+
+  // Enable the track.
+  EXPECT_CALL(*scrollbar, PaintPart(_, THUMB, _)).Times(0);
+  EXPECT_CALL(*scrollbar, PaintPart(_, TRACK, _)).Times(1);
+  scrollbar->set_needs_paint_thumb(false);
+  scrollbar->set_needs_paint_track(true);
+  scrollbar_layer->Update();
+  Mock::VerifyAndClearExpectations(scrollbar);
+}
+
+}  // namespace
+}  // namespace cc