Lock video controls' position during fullscreen

Problem:
Video controls can be scrolled (moved) when
an Android WebView does fullscreen-video.

Solution:
When visual viewport's scrolling is disabled
using setUserScrollable(false, false), do
also disable over-scrolling (do not send
overscroll-events to the Android WebView).

BUG=448738
TEST=
  1. Start com.android.browser and go to
     http://robnyman.github.io/fullscreen/ .
  2. Start video playback.
  3. Go fullscreen on video.
  4. Fling the screen.
  5. Notice 1: Video controls cannot move.
  6. Notice 2: No "over glow" (compare with
     Android Chrome or Lollipop's WebView).

CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1228423002

Cr-Commit-Position: refs/heads/master@{#343675}

2 files changed, 76 insertions, 6 deletions

diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 5b52d07..49d1821 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1499,19 +1499,21 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
 
   active_tree_->GetViewportSelection(&metadata.selection);
 
-  LayerImpl* root_layer_for_overflow = OuterViewportScrollLayer()
-                                           ? OuterViewportScrollLayer()
-                                           : InnerViewportScrollLayer();
-  if (root_layer_for_overflow) {
+  if (OuterViewportScrollLayer()) {
     metadata.root_overflow_x_hidden =
-        !root_layer_for_overflow->user_scrollable_horizontal();
+        !OuterViewportScrollLayer()->user_scrollable_horizontal();
     metadata.root_overflow_y_hidden =
-        !root_layer_for_overflow->user_scrollable_vertical();
+        !OuterViewportScrollLayer()->user_scrollable_vertical();
   }
 
   if (!InnerViewportScrollLayer())
     return metadata;
 
+  metadata.root_overflow_x_hidden |=
+      !InnerViewportScrollLayer()->user_scrollable_horizontal();
+  metadata.root_overflow_y_hidden |=
+      !InnerViewportScrollLayer()->user_scrollable_vertical();
+
   // TODO(miletus) : Change the metadata to hold ScrollOffset.
   metadata.root_scroll_offset = gfx::ScrollOffsetToVector2dF(
       active_tree_->TotalScrollOffset());
@@ -2749,6 +2751,15 @@ InputHandlerScrollResult LayerTreeHostImpl::ScrollBy(
     accumulated_root_overscroll_.set_y(0);
   gfx::Vector2dF unused_root_delta(scroll_state.delta_x(),
                                    scroll_state.delta_y());
+
+  // When inner viewport is unscrollable, disable overscrolls.
+  if (InnerViewportScrollLayer()) {
+    if (!InnerViewportScrollLayer()->user_scrollable_horizontal())
+      unused_root_delta.set_x(0);
+    if (!InnerViewportScrollLayer()->user_scrollable_vertical())
+      unused_root_delta.set_y(0);
+  }
+
   accumulated_root_overscroll_ += unused_root_delta;
 
   bool did_scroll_top_controls =
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index e32780f..127679c 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2216,6 +2216,39 @@ TEST_F(LayerTreeHostImplTest, CompositorFrameMetadata) {
     EXPECT_TRUE(metadata.root_overflow_y_hidden);
   }
 
+  // Re-enable scrollability and verify that overflows are no longer hidden.
+  {
+    host_impl_->active_tree()
+        ->OuterViewportScrollLayer()
+        ->set_user_scrollable_horizontal(true);
+    host_impl_->active_tree()
+        ->OuterViewportScrollLayer()
+        ->set_user_scrollable_vertical(true);
+    CompositorFrameMetadata metadata =
+        host_impl_->MakeCompositorFrameMetadata();
+    EXPECT_FALSE(metadata.root_overflow_x_hidden);
+    EXPECT_FALSE(metadata.root_overflow_y_hidden);
+  }
+
+  // Root "overflow: hidden" properties should also be reflected on the
+  // inner viewport scroll layer.
+  {
+    host_impl_->active_tree()
+        ->InnerViewportScrollLayer()
+        ->set_user_scrollable_horizontal(false);
+    CompositorFrameMetadata metadata =
+        host_impl_->MakeCompositorFrameMetadata();
+    EXPECT_TRUE(metadata.root_overflow_x_hidden);
+    EXPECT_FALSE(metadata.root_overflow_y_hidden);
+
+    host_impl_->active_tree()
+        ->InnerViewportScrollLayer()
+        ->set_user_scrollable_vertical(false);
+    metadata = host_impl_->MakeCompositorFrameMetadata();
+    EXPECT_TRUE(metadata.root_overflow_x_hidden);
+    EXPECT_TRUE(metadata.root_overflow_y_hidden);
+  }
+
   // Page scale should update metadata correctly (shrinking only the viewport).
   host_impl_->ScrollBegin(gfx::Point(), InputHandler::GESTURE);
   host_impl_->PinchGestureBegin();
@@ -7660,6 +7693,32 @@ TEST_F(LayerTreeHostImplVirtualViewportTest,
   host_impl_->ScrollEnd();
 }
 
+TEST_F(LayerTreeHostImplVirtualViewportTest,
+       NoOverscrollWhenInnerViewportCantScroll) {
+  InputHandlerScrollResult scroll_result;
+  gfx::Size content_size = gfx::Size(100, 160);
+  gfx::Size outer_viewport = gfx::Size(50, 80);
+  gfx::Size inner_viewport = gfx::Size(25, 40);
+  SetupVirtualViewportLayers(content_size, outer_viewport, inner_viewport);
+  DrawFrame();
+
+  // Make inner viewport unscrollable.
+  LayerImpl* inner_scroll = host_impl_->InnerViewportScrollLayer();
+  inner_scroll->set_user_scrollable_horizontal(false);
+  inner_scroll->set_user_scrollable_vertical(false);
+
+  // Ensure inner viewport doesn't react to scrolls (test it's unscrollable).
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), inner_scroll->CurrentScrollOffset());
+  EXPECT_EQ(InputHandler::SCROLL_STARTED,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::GESTURE));
+  scroll_result = host_impl_->ScrollBy(gfx::Point(), gfx::Vector2dF(0, 100));
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), inner_scroll->CurrentScrollOffset());
+
+  // When inner viewport is unscrollable, a fling gives zero overscroll.
+  EXPECT_FALSE(scroll_result.did_overscroll_root);
+  EXPECT_EQ(gfx::Vector2dF(), host_impl_->accumulated_root_overscroll());
+}
+
 class LayerTreeHostImplWithImplicitLimitsTest : public LayerTreeHostImplTest {
  public:
   void SetUp() override {