Update from https://crrev.com/304715

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 0b9d976cd25cb65553060b7076a82d19ec5a2e54..51377d249d1657e8b38e87f327f89766080f4a4c 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2319,6 +2319,8 @@ class LayerTreeHostImplTopControlsTest : public LayerTreeHostImplTest {
       const gfx::Size& outer_viewport_size,
       const gfx::Size& scroll_layer_size) {
     CreateHostImpl(settings_, CreateOutputSurface());
+    host_impl_->SetTopControlsLayoutHeight(
+        settings_.top_controls_height);
 
     scoped_ptr<LayerImpl> root =
         LayerImpl::Create(host_impl_->active_tree(), 1);
@@ -2364,8 +2366,6 @@ class LayerTreeHostImplTopControlsTest : public LayerTreeHostImplTest {
         outer_viewport_scroll_layer_id);
 
     host_impl_->SetViewportSize(inner_viewport_size);
-    host_impl_->SetTopControlsLayoutHeight(
-        settings_.top_controls_height);
     LayerImpl* root_clip_ptr = host_impl_->active_tree()->root_layer();
     EXPECT_EQ(inner_viewport_size, root_clip_ptr->bounds());
   }
@@ -2402,6 +2402,81 @@ TEST_F(LayerTreeHostImplTopControlsTest, ScrollTopControlsByFractionalAmount) {
             inner_viewport_scroll_layer->FixedContainerSizeDelta());
 }
 
+// In this test, the outer viewport is initially unscrollable. We test that a
+// scroll initiated on the inner viewport, causing the top controls to show and
+// thus making the outer viewport scrollable, still scrolls the outer viewport.
+TEST_F(LayerTreeHostImplTopControlsTest,
+    TopControlsOuterViewportBecomesScrollable) {
+  SetupTopControlsAndScrollLayerWithVirtualViewport(
+      gfx::Size(10, 50), gfx::Size(10, 50), gfx::Size(10, 100));
+  DrawFrame();
+
+  LayerImpl *inner_scroll =
+      host_impl_->active_tree()->InnerViewportScrollLayer();
+  LayerImpl *inner_container =
+      host_impl_->active_tree()->InnerViewportContainerLayer();
+  LayerImpl *outer_scroll =
+      host_impl_->active_tree()->OuterViewportScrollLayer();
+  LayerImpl *outer_container =
+      host_impl_->active_tree()->OuterViewportContainerLayer();
+
+  // Need SetDrawsContent so ScrollBegin's hit test finds an actual layer.
+  outer_scroll->SetDrawsContent(true);
+  host_impl_->active_tree()->SetPageScaleFactorAndLimits(2.f, 1.f, 2.f);
+
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, 50.f));
+
+  // The entire scroll delta should have been used to hide the top controls.
+  // The viewport layers should be resized back to their full sizes.
+  EXPECT_EQ(0.f,
+      host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(0.f, inner_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(100.f, inner_container->BoundsForScrolling().height());
+  EXPECT_EQ(100.f, outer_container->BoundsForScrolling().height());
+
+  // The inner viewport should be scrollable by 50px * page_scale.
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, 100.f));
+  EXPECT_EQ(50.f, inner_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(0.f, outer_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(gfx::ScrollOffset(), outer_scroll->MaxScrollOffset());
+
+  host_impl_->ScrollEnd();
+
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
+  EXPECT_EQ(host_impl_->CurrentlyScrollingLayer(), inner_scroll);
+
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, -50.f));
+
+  // The entire scroll delta should have been used to show the top controls.
+  // The outer viewport should be resized to accomodate and scrolled to the
+  // bottom of the document to keep the viewport in place.
+  EXPECT_EQ(50.f,
+      host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(50.f, outer_container->BoundsForScrolling().height());
+  EXPECT_EQ(50.f, inner_container->BoundsForScrolling().height());
+  EXPECT_EQ(25.f, outer_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(25.f, inner_scroll->TotalScrollOffset().y());
+
+  // Now when we continue scrolling, make sure the outer viewport gets scrolled
+  // since it wasn't scrollable when the scroll began.
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, -20.f));
+  EXPECT_EQ(15.f, outer_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(25.f, inner_scroll->TotalScrollOffset().y());
+
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, -30.f));
+  EXPECT_EQ(0.f, outer_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(25.f, inner_scroll->TotalScrollOffset().y());
+
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0.f, -50.f));
+  host_impl_->ScrollEnd();
+
+  EXPECT_EQ(0.f, outer_scroll->TotalScrollOffset().y());
+  EXPECT_EQ(0.f, inner_scroll->TotalScrollOffset().y());
+}
+
 // Test that the fixed position container delta is appropriately adjusted
 // by the top controls showing/hiding and page scale doesn't affect it.
 TEST_F(LayerTreeHostImplTopControlsTest, FixedContainerDelta) {