Mac: Don't repaint scrollbars every frame

cc/layers/painted_scrollbar_layer_impl_unittest.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 "cc/layers/painted_scrollbar_layer_impl.h"
 
 #include "cc/quads/draw_quad.h"
+#include "cc/quads/texture_draw_quad.h"
 #include "cc/test/layer_test_common.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace cc {
 namespace {
 
 TEST(PaintedScrollbarLayerImplTest, Occlusion) {
   gfx::Size layer_size(10, 1000);
   float scale = 2.f;
   gfx::Size scaled_layer_size(20, 2000);
   gfx::Size viewport_size(1000, 1000);
+  float thumb_opacity = 0.2f;
 
   LayerTestCommon::LayerImplTest impl;
 
   SkBitmap thumb_sk_bitmap;
   thumb_sk_bitmap.allocN32Pixels(10, 10);
   thumb_sk_bitmap.setImmutable();
   UIResourceId thumb_uid = 5;
   UIResourceBitmap thumb_bitmap(thumb_sk_bitmap);
   impl.host_impl()->CreateUIResource(thumb_uid, thumb_bitmap);
 
@@ skipping 14 matching lines @@
       scale, scaled_layer_size);
   scrollbar_layer_impl->SetDrawsContent(true);
   scrollbar_layer_impl->SetThumbThickness(layer_size.width());
   scrollbar_layer_impl->SetThumbLength(500);
   scrollbar_layer_impl->SetTrackLength(layer_size.height());
   scrollbar_layer_impl->SetCurrentPos(100.f / 4);
   scrollbar_layer_impl->SetClipLayerLength(100.f);
   scrollbar_layer_impl->SetScrollLayerLength(200.f);
   scrollbar_layer_impl->set_track_ui_resource_id(track_uid);
   scrollbar_layer_impl->set_thumb_ui_resource_id(thumb_uid);
+  scrollbar_layer_impl->set_thumb_opacity(thumb_opacity);
 
   impl.CalcDrawProps(viewport_size);
 
   gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
   EXPECT_EQ(gfx::Rect(0, 500 / 4, 10, layer_size.height() / 2).ToString(),
             thumb_rect.ToString());
 
   {
     SCOPED_TRACE("No occlusion");
     gfx::Rect occluded;
     impl.AppendQuadsWithOcclusion(scrollbar_layer_impl, occluded);
 
     size_t partially_occluded_count = 0;
     LayerTestCommon::VerifyQuadsAreOccluded(
         impl.quad_list(), occluded, &partially_occluded_count);
     EXPECT_EQ(2u, impl.quad_list().size());
     EXPECT_EQ(0u, partially_occluded_count);
 
     // Note: this is also testing that the thumb and track are both
     // scaled by the internal contents scale.  It's not occlusion-related
     // but is easy to verify here.
-    const DrawQuad* thumb_quad = impl.quad_list().ElementAt(0);
-    const DrawQuad* track_quad = impl.quad_list().ElementAt(1);
+    const DrawQuad* thumb_draw_quad = impl.quad_list().ElementAt(0);
+    const DrawQuad* track_draw_quad = impl.quad_list().ElementAt(1);
+
+    EXPECT_EQ(DrawQuad::TEXTURE_CONTENT, thumb_draw_quad->material);
+    EXPECT_EQ(DrawQuad::TEXTURE_CONTENT, track_draw_quad->material);
+
+    const TextureDrawQuad* thumb_quad =
+        TextureDrawQuad::MaterialCast(thumb_draw_quad);
+    const TextureDrawQuad* track_quad =
+        TextureDrawQuad::MaterialCast(track_draw_quad);
 
     gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
     EXPECT_EQ(track_quad->rect.ToString(),
               gfx::Rect(scaled_layer_size).ToString());
     EXPECT_EQ(track_quad->opaque_rect.ToString(),
               gfx::Rect(scaled_layer_size).ToString());
     EXPECT_EQ(track_quad->visible_rect.ToString(),
               gfx::Rect(scaled_layer_size).ToString());
     EXPECT_EQ(thumb_quad->rect.ToString(), scaled_thumb_rect.ToString());
     EXPECT_EQ(thumb_quad->visible_rect.ToString(),
               scaled_thumb_rect.ToString());
+    EXPECT_EQ(thumb_quad->visible_rect.ToString(),
+              scaled_thumb_rect.ToString());
+    for (size_t i = 0; i < 4; ++i) {
+      EXPECT_EQ(thumb_opacity, thumb_quad->vertex_opacity[i]);
+      EXPECT_EQ(1.f, track_quad->vertex_opacity[i]);
+    }
   }
 
   {
     SCOPED_TRACE("Full occlusion");
     gfx::Rect occluded(scrollbar_layer_impl->visible_layer_rect());
     impl.AppendQuadsWithOcclusion(scrollbar_layer_impl, occluded);
 
     LayerTestCommon::VerifyQuadsExactlyCoverRect(impl.quad_list(), gfx::Rect());
     EXPECT_EQ(impl.quad_list().size(), 0u);
   }
 
   {
     SCOPED_TRACE("Partial occlusion");
     gfx::Rect occluded(0, 0, 5, 1000);
     impl.AppendQuadsWithOcclusion(scrollbar_layer_impl, occluded);
 
     size_t partially_occluded_count = 0;
     LayerTestCommon::VerifyQuadsAreOccluded(
         impl.quad_list(), occluded, &partially_occluded_count);
     // The layer outputs two quads, which is partially occluded.
     EXPECT_EQ(2u, impl.quad_list().size());
     EXPECT_EQ(2u, partially_occluded_count);
   }
 }
 
 }  // namespace
 }  // namespace cc