Adding support for blending in cc::SoftwareRenderer

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 7a492a1d5bfde2cc2e11afa89d82057645b60256..7c0354dbef7ddf84e1cd47e732a339bc8a474af2 100644
--- a/cc/trees/layer_tree_host_pixeltest_blending.cc
+++ b/cc/trees/layer_tree_host_pixeltest_blending.cc
@@ -5,6 +5,7 @@
 #include "cc/layers/solid_color_layer.h"
 #include "cc/layers/texture_layer.h"
 #include "cc/test/layer_tree_pixel_test.h"
+#include "cc/test/pixel_test.h"
 
 #if !defined(OS_ANDROID)
 
@@ -23,6 +24,13 @@ SkXfermode::Mode const kBlendModes[] = {
 
 const int kBlendModesCount = arraysize(kBlendModes);
 
+// All pixels can be off by one, but any more than that is an error.
+class FuzzyPixelOffByOneComparator : public FuzzyPixelComparator {

[enne (OOO), 2014/09/05 17:49:08]

I feel like this is duplicated elsewhere.  Can you move this to some common
location?

[rosca, 2014/09/05 20:52:27]

Done.

+ public:
+  explicit FuzzyPixelOffByOneComparator(bool discard_alpha)
+      : FuzzyPixelComparator(discard_alpha, 100.f, 0.f, 1.f, 1, 0) {}
+};
+
 class LayerTreeHostBlendingPixelTest : public LayerTreePixelTest {
  protected:
   void RunBlendingWithRootPixelTestType(PixelTestType type) {
@@ -43,6 +51,9 @@ class LayerTreeHostBlendingPixelTest : public LayerTreePixelTest {
       green_lane->SetBlendMode(kBlendModes[i]);
     }
 
+    if (type == SOFTWARE_WITH_BITMAP)

[enne (OOO), 2014/09/05 17:49:08]

I'd be ok with making all the blending tests use an off-by-one comparator.  It's
not clear to me that the mesa version is right and the software renderer version
is wrong.

[rosca, 2014/09/05 20:52:28]

Done.

+      pixel_comparator_.reset(new FuzzyPixelOffByOneComparator(true));
+
     RunPixelTest(type,
                  background,
                  base::FilePath(FILE_PATH_LITERAL("blending_with_root.png")));
@@ -72,6 +83,9 @@ class LayerTreeHostBlendingPixelTest : public LayerTreePixelTest {
       green_lane->SetBlendMode(kBlendModes[i]);
     }
 
+    if (type == SOFTWARE_WITH_BITMAP)
+      pixel_comparator_.reset(new FuzzyPixelOffByOneComparator(true));
+
     RunPixelTest(type,
                  root,
                  base::FilePath(FILE_PATH_LITERAL("blending_transparent.png")));
@@ -82,6 +96,10 @@ TEST_F(LayerTreeHostBlendingPixelTest, BlendingWithRoot_GL) {
   RunBlendingWithRootPixelTestType(GL_WITH_BITMAP);
 }
 
+TEST_F(LayerTreeHostBlendingPixelTest, BlendingWithRoot_Software) {
+  RunBlendingWithRootPixelTestType(SOFTWARE_WITH_BITMAP);
+}
+
 TEST_F(LayerTreeHostBlendingPixelTest, BlendingWithBackgroundFilter) {
   const int kLaneWidth = 15;
   const int kLaneHeight = kBlendModesCount * kLaneWidth;
@@ -114,6 +132,10 @@ TEST_F(LayerTreeHostBlendingPixelTest, BlendingWithTransparent_GL) {
   RunBlendingWithTransparentPixelTestType(GL_WITH_BITMAP);
 }
 
+TEST_F(LayerTreeHostBlendingPixelTest, BlendingWithTransparent_Software) {
+  RunBlendingWithTransparentPixelTestType(SOFTWARE_WITH_BITMAP);
+}
+
 }  // namespace
 }  // namespace cc