[cc] Add SkBlendMode::kDstIn support to cc::Layer

cc/trees/layer_tree_host_pixeltest_blending.cc

Index: cc/trees/layer_tree_host_pixeltest_blending.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_blending.cc b/cc/trees/layer_tree_host_pixeltest_blending.cc
index d2eb0a7b3ea1890a1ecbb4c0987339758892f792..d1b179ce80dcc5536ab5104c157b6ce67b007a63 100644
--- a/cc/trees/layer_tree_host_pixeltest_blending.cc
+++ b/cc/trees/layer_tree_host_pixeltest_blending.cc
@@ -24,7 +24,8 @@ SkBlendMode const kBlendModes[] = {
     SkBlendMode::kSoftLight, SkBlendMode::kDifference,
     SkBlendMode::kExclusion, SkBlendMode::kMultiply,
     SkBlendMode::kHue,       SkBlendMode::kSaturation,
-    SkBlendMode::kColor,     SkBlendMode::kLuminosity};
+    SkBlendMode::kColor,     SkBlendMode::kLuminosity,
+    SkBlendMode::kDstIn};
 
 SkColor kCSSTestColors[] = {
     0xffff0000,  // red
@@ -180,7 +181,7 @@ class LayerTreeHostBlendingPixelTest : public LayerTreeHostPixelResourceTest {
                                  int lane_height,
                                  scoped_refptr<Layer> background,
                                  RenderPassOptions flags) {
-    const int kLanesCount = kBlendModesCount + 4;
+    const int kLanesCount = kBlendModesCount + 6;
     const SkColor kMiscOpaqueColor = 0xffc86464;
     const SkColor kMiscTransparentColor = 0x80c86464;
     const SkBlendMode kCoeffBlendMode = SkBlendMode::kScreen;
@@ -206,6 +207,12 @@ class LayerTreeHostBlendingPixelTest : public LayerTreeHostPixelResourceTest {
       } else if (i == kBlendModesCount + 3) {
         blend_mode = kShaderBlendMode;
         color = kMiscTransparentColor;
+      } else if (i == kBlendModesCount + 4) {
+        blend_mode = SkBlendMode::kDstIn;
+        opacity = 0.5f;
+      } else if (i == kBlendModesCount + 5) {
+        blend_mode = SkBlendMode::kDstIn;
+        color = kMiscTransparentColor;
       }
 
       scoped_refptr<SolidColorLayer> lane =
@@ -213,7 +220,8 @@ class LayerTreeHostBlendingPixelTest : public LayerTreeHostPixelResourceTest {
       lane->SetBlendMode(blend_mode);
       lane->SetOpacity(opacity);
       lane->SetForceRenderSurfaceForTesting(true);
-      if (flags & kUseMasks)
+      // Layers with kDstIn blend mode with a mask is not supported.
+      if (flags & kUseMasks && blend_mode != SkBlendMode::kDstIn)
         SetupMaskLayer(lane);
       if (flags & kUseColorMatrix) {
         SetupColorMatrix(lane);
@@ -226,19 +234,19 @@ class LayerTreeHostBlendingPixelTest : public LayerTreeHostPixelResourceTest {
                                  const base::FilePath::CharType* expected_path,
                                  RenderPassOptions flags) {
     const int kLaneWidth = 8;
-    const int kLaneHeight = kLaneWidth * kCSSTestColorsCount;
-    const int kRootSize = kLaneHeight;
+    const int kRootWidth = kLaneWidth * (kBlendModesCount + 6);
+    const int kRootHeight = kLaneWidth * kCSSTestColorsCount;
     InitializeFromTestCase(type);
 
-    scoped_refptr<SolidColorLayer> root =
-        CreateSolidColorLayer(gfx::Rect(kRootSize, kRootSize), SK_ColorWHITE);
+    scoped_refptr<SolidColorLayer> root = CreateSolidColorLayer(
+        gfx::Rect(kRootWidth, kRootHeight), SK_ColorWHITE);
     scoped_refptr<Layer> background =
-        CreateColorfulBackdropLayer(kRootSize, kRootSize);
+        CreateColorfulBackdropLayer(kRootWidth, kRootHeight);
 
     background->SetIsRootForIsolatedGroup(true);
     root->AddChild(background);
 
-    CreateBlendingColorLayers(kLaneWidth, kLaneHeight, background.get(), flags);
+    CreateBlendingColorLayers(kLaneWidth, kRootHeight, background.get(), flags);
 
     this->force_antialiasing_ = (flags & kUseAntialiasing);
     this->force_blending_with_shaders_ = (flags & kForceShaders);