Determine mask UVs based on texture size

cc/trees/layer_tree_host_pixeltest_masks.cc

Index: cc/trees/layer_tree_host_pixeltest_masks.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_masks.cc b/cc/trees/layer_tree_host_pixeltest_masks.cc
index eed99f6a625e026151c71b62a9767b34c683bc5e..583df67350ac788f8d82e86babfc698c729736a6 100644
--- a/cc/trees/layer_tree_host_pixeltest_masks.cc
+++ b/cc/trees/layer_tree_host_pixeltest_masks.cc
@@ -148,6 +148,34 @@ TEST_P(LayerTreeHostMasksPixelTest, MaskOfClippedLayer) {
       base::FilePath(FILE_PATH_LITERAL("mask_of_clipped_layer.png")));
 }
 
+TEST_P(LayerTreeHostMasksPixelTest, MaskOfLargerLayer) {
+  scoped_refptr<SolidColorLayer> background =
+      CreateSolidColorLayer(gfx::Rect(100, 100), SK_ColorWHITE);
+
+  scoped_refptr<SolidColorLayer> green = CreateSolidColorLayerWithBorder(
+      gfx::Rect(0, 0, 100, 100), kCSSGreen, 1, SK_ColorBLACK);
+  background->AddChild(green);
+
+  gfx::Size mask_bounds(40, 40);

[enne (OOO), 2017/05/02 21:31:37]

Feel free to take or leave this suggestion, but if you made the mask bounds 50,
50, would that make it stretch but line up on pixel boundaries, so all tests
ended with the same result?

[ericrk, 2017/05/04 19:23:53]

Per discussion, doesn't quite work. Added fuzzy comparison for BITMAP provider.

+  MaskContentLayerClient client(mask_bounds);
+  scoped_refptr<PictureLayer> mask = PictureLayer::Create(&client);
+  mask->SetBounds(mask_bounds);
+  mask->SetIsDrawable(true);
+  mask->SetLayerMaskType(Layer::LayerMaskType::SINGLE_TEXTURE_MASK);

[sunxd, 2017/05/03 15:14:13]

I made a recent change that makes pixeltest tests both SINGLE_TEXTURE_MASK and
MULTI_TEXTURE_MASK.

Can you change this line to:

mask->SetLayerMaskType(mask_type_);

[ericrk, 2017/05/04 19:23:53]

done. Thanks!

+  green->SetMaskLayer(mask.get());
+
+  if (raster_buffer_provider_type_ == RASTER_BUFFER_PROVIDER_TYPE_BITMAP) {
+    // Bitmap produces a sharper (but equivalent sized) mask.
+    RunPixelResourceTest(
+        background,
+        base::FilePath(FILE_PATH_LITERAL("mask_of_larger_layer_bitmap.png")));
+  } else {
+    RunPixelResourceTest(
+        background,
+        base::FilePath(FILE_PATH_LITERAL("mask_of_larger_layer.png")));
+  }
+}
+
 class CheckerContentLayerClient : public ContentLayerClient {
  public:
   CheckerContentLayerClient(const gfx::Size& bounds,