cc: Do not allow gesture-scrolling 'overflow[-{x|y}]:hidden' layers.

cc/layers/layer_impl_unittest.cc

Index: cc/layers/layer_impl_unittest.cc
diff --git a/cc/layers/layer_impl_unittest.cc b/cc/layers/layer_impl_unittest.cc
index 83cd346e4778fe5bae9ec11bcbd1d50949c5b37b..b05f6e7e2da0e1b04ffa0322720c6259c229cb7c 100644
--- a/cc/layers/layer_impl_unittest.cc
+++ b/cc/layers/layer_impl_unittest.cc
@@ -547,5 +547,19 @@ TEST_F(LayerImplScrollTest, ApplySentScrollsWithAcceptingDelegate) {
   EXPECT_VECTOR_EQ(gfx::Vector2d(), layer()->sent_scroll_delta());
 }
 
+TEST_F(LayerImplScrollTest, ScrollUserUnscrollableLayer) {
+  gfx::Vector2d max_scroll_offset(50, 80);
+  gfx::Vector2d scroll_offset(10, 5);
+  gfx::Vector2dF scroll_delta(20.5f, 8.5f);
+
+  layer()->SetUserScrollable(true, false);
+  layer()->SetMaxScrollOffset(max_scroll_offset);
+  layer()->SetScrollOffset(scroll_offset);
+  gfx::Vector2dF unscrolled = layer()->ScrollBy(scroll_delta);
+
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(0, 8.5f), unscrolled);
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(30.5f, 5), layer()->TotalScrollOffset());
+}
+
 }  // namespace
 }  // namespace cc