Implement on demand quad rasterization for PicturePiles.

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index a99f2a91efbbab5c85499499d1ea0360a7751da8..5384cdf2deb1455e00f385b365c5e6b4ba1f64a3 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -1047,10 +1047,12 @@ public:
 
         switch (impl->active_tree()->source_frame_number()) {
         case 0:
-            // Number of textures should be one for each layer
-            ASSERT_EQ(2, context->NumTextures());
-            // Number of textures used for commit should be one for each layer.
-            EXPECT_EQ(2, context->NumUsedTextures());
+            // Number of textures should be one for each layer plus an auxiliary
+            // texture for on-demand rasterization.
+            ASSERT_EQ(3, context->NumTextures());
+            // Number of textures used for commit should be one for each layer
+            // plus the auxiliary one on startup.
+            EXPECT_EQ(3, context->NumUsedTextures());
             // Verify that used texture is correct.
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(0)));
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(1)));
@@ -1059,17 +1061,19 @@ public:
             postSetNeedsCommitToMainThread();
             break;
         case 1:
-            // Number of textures should be doubled as the first textures
-            // are used by impl thread and cannot by used for update.
-            ASSERT_EQ(4, context->NumTextures());
+            // Number of textures should be doubled (excepting the auxiliary)
+            // as the first textures are used by impl thread and cannot by used
+            // for update.
+            ASSERT_EQ(5, context->NumTextures());
             // Number of textures used for commit should still be one for each layer.
             EXPECT_EQ(2, context->NumUsedTextures());
             // First textures should not have been used.
-            EXPECT_FALSE(context->UsedTexture(context->TextureAt(0)));
+            // Index 0 is used by the auxiliary texture.
             EXPECT_FALSE(context->UsedTexture(context->TextureAt(1)));
+            EXPECT_FALSE(context->UsedTexture(context->TextureAt(2)));
             // New textures should have been used.
-            EXPECT_TRUE(context->UsedTexture(context->TextureAt(2)));
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(3)));
+            EXPECT_TRUE(context->UsedTexture(context->TextureAt(4)));
 
             context->ResetUsedTextures();
             postSetNeedsCommitToMainThread();
@@ -1179,10 +1183,12 @@ public:
 
         switch (impl->active_tree()->source_frame_number()) {
         case 0:
-            // Number of textures should be one for each layer.
-            ASSERT_EQ(4, context->NumTextures());
-            // Number of textures used for commit should be one for each layer.
-            EXPECT_EQ(4, context->NumUsedTextures());
+            // Number of textures should be one for each layer plus an auxiliary
+            // texture for on-demand rasterization.
+            ASSERT_EQ(5, context->NumTextures());
+            // Number of textures used for commit should be one for each layer
+            // plus the auxiliary one on startup.
+            EXPECT_EQ(5, context->NumUsedTextures());
             // Verify that used textures are correct.
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(0)));
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(1)));
@@ -1193,42 +1199,45 @@ public:
             postSetNeedsCommitToMainThread();
             break;
         case 1:
-            // Number of textures should be two for each content layer and one
+            // Number of textures should be two for each content layer,
+            // an auxiliary one for on-demand rasterization and one
             // for each scrollbar, since they always do a partial update.
-            ASSERT_EQ(6, context->NumTextures());
+            ASSERT_EQ(7, context->NumTextures());
             // Number of textures used for commit should be one for each content
             // layer, and one for the scrollbar layer that paints.
             EXPECT_EQ(3, context->NumUsedTextures());
 
             // First content textures should not have been used.
-            EXPECT_FALSE(context->UsedTexture(context->TextureAt(0)));
+            // Index 0 is used by the auxiliary texture.
             EXPECT_FALSE(context->UsedTexture(context->TextureAt(1)));
-            // The non-painting scrollbar's texture wasn't updated.
             EXPECT_FALSE(context->UsedTexture(context->TextureAt(2)));
+            // The non-painting scrollbar's texture wasn't updated.
+            EXPECT_FALSE(context->UsedTexture(context->TextureAt(3)));
             // The painting scrollbar's partial update texture was used.
-            EXPECT_TRUE(context->UsedTexture(context->TextureAt(3)));
-            // New textures should have been used.
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(4)));
+            // New textures should have been used.
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(5)));
+            EXPECT_TRUE(context->UsedTexture(context->TextureAt(6)));
 
             context->ResetUsedTextures();
             postSetNeedsCommitToMainThread();
             break;
         case 2:
-            // Number of textures should be two for each content layer and one
+            // Number of textures should be two for each content layer,
+            // an auxiliary one for on-demand rasterization and one
             // for each scrollbar, since they always do a partial update.
-            ASSERT_EQ(6, context->NumTextures());
+            ASSERT_EQ(7, context->NumTextures());
             // Number of textures used for commit should be one for each content
             // layer, and one for the scrollbar layer that paints.
             EXPECT_EQ(3, context->NumUsedTextures());
 
             // The non-painting scrollbar's texture wasn't updated.
-            EXPECT_FALSE(context->UsedTexture(context->TextureAt(2)));
+            EXPECT_FALSE(context->UsedTexture(context->TextureAt(3)));
             // The painting scrollbar does a partial update.
-            EXPECT_TRUE(context->UsedTexture(context->TextureAt(3)));
-            // One content layer does a partial update also.
             EXPECT_TRUE(context->UsedTexture(context->TextureAt(4)));
-            EXPECT_FALSE(context->UsedTexture(context->TextureAt(5)));
+            // One content layer does a partial update also.
+            EXPECT_TRUE(context->UsedTexture(context->TextureAt(5)));
+            EXPECT_FALSE(context->UsedTexture(context->TextureAt(6)));
 
             context->ResetUsedTextures();
             postSetNeedsCommitToMainThread();