GSB uses delta_hints to calculate scrolling chain.

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index 5a3f510b15522c8a75a9693b8c7c8f4ee5b8a924..a4bc86fa8b7f2ecdb8058b1e2a0cd7321c6c5d76 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -6245,13 +6245,9 @@ TEST_F(LayerTreeHostImplTest, ScrollNonAxisAlignedRotatedLayer) {
     host_impl_->ScrollEnd(EndState().get());
 
     // The child layer shouldn't have scrolled.
-    gfx::Vector2d expected_scroll_delta(
-        0, -gesture_scroll_delta.x() *
-               std::sin(MathUtil::Deg2Rad(child_layer_angle)));
     std::unique_ptr<ScrollAndScaleSet> scroll_info =
         host_impl_->ProcessScrollDeltas();
-    EXPECT_TRUE(ScrollInfoContains(*scroll_info.get(), child_scroll_id,
-                                   expected_scroll_delta));
+    ExpectNone(*scroll_info.get(), child_scroll_id);

[bokan, 2017/06/19 21:43:17]

What's this change about? The comment above says the layer shouldn't have
scrolled but it used to check that it does? Was the test before incorrect? Does
your patch fix the behavior?

[sahel, 2017/06/22 16:34:17]

As we discussed the comment is incorrect, I confirmed it with tdresser@ as well.
The child layer should scroll, so I left the test expectation as it is and
corrected the comment. I had to change layer_tree_host_impl.cc to take
transformations into account in canConsumeDelta function.  

[bokan, 2017/06/22 21:44:37]

Acknowledged.

 
     // The root scroll layer shouldn't have scrolled.
     ExpectNone(*scroll_info.get(), scroll_layer->element_id());
@@ -10923,12 +10919,14 @@ TEST_F(LayerTreeHostImplTest, SecondScrollAnimatedBeginNotIgnored) {
   const gfx::Size viewport_size(50, 100);
   CreateBasicVirtualViewportLayers(viewport_size, content_size);
 
-  EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD,
-            host_impl_->ScrollAnimatedBegin(gfx::Point()).thread);
+  EXPECT_EQ(
+      InputHandler::SCROLL_ON_IMPL_THREAD,
+      host_impl_->ScrollAnimatedBegin(BeginState(gfx::Point()).get()).thread);
 
   // The second ScrollAnimatedBegin should not get ignored.
-  EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD,
-            host_impl_->ScrollAnimatedBegin(gfx::Point()).thread);
+  EXPECT_EQ(
+      InputHandler::SCROLL_ON_IMPL_THREAD,
+      host_impl_->ScrollAnimatedBegin(BeginState(gfx::Point()).get()).thread);
 }
 
 // Verfify that a smooth scroll animation doesn't jump when UpdateTarget gets