cc: Ignore offscreen tiles for activation

Remove the overenthusiastic DCHECK from PictureLayerImpl to make sure
that every tile that intersects the visible content rect also has a
distance to the viewport of zero.  Because the projection of the
viewport is done more precisely than the enclosing rect for the visible
content rect, it may be possible for a tile to be outside the viewport
but inside the visible content rect.

Therefore, the current DCHECKS are bogus.  Instead, skip these tiles
because they're not truly required for activation.

R=reveman@chromium.org
BUG=243437

Review URL: https://chromiumcodereview.appspot.com/16160005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203063 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 84 insertions, 8 deletions

diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index e3b2c3b..6dc7e63 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -684,11 +684,15 @@ void PictureLayerImpl::MarkVisibleResourcesAsRequired() const {
          ++iter) {
       if (!*iter || !iter->tile_version().IsReadyToDraw())
         continue;
+
+      // This iteration is over the visible content rect which is potentially
+      // less conservative than projecting the viewport into the layer.
+      // Ignore tiles that are know to be outside the viewport.
+      if (iter->priority(PENDING_TREE).distance_to_visible_in_pixels != 0)
+        continue;
+
       missing_region.Subtract(iter.geometry_rect());
       iter->mark_required_for_activation();
-
-      DCHECK_EQ(iter->priority(PENDING_TREE).distance_to_visible_in_pixels, 0);
-      DCHECK_EQ(iter->priority(PENDING_TREE).time_to_visible_in_seconds, 0);
     }
   }
 
@@ -699,15 +703,21 @@ void PictureLayerImpl::MarkVisibleResourcesAsRequired() const {
        iter;
        ++iter) {
     // A null tile (i.e. missing recording) can just be skipped.
+    if (!*iter)
+      continue;
+
+    // This iteration is over the visible content rect which is potentially
+    // less conservative than projecting the viewport into the layer.
+    // Ignore tiles that are know to be outside the viewport.
+    if (iter->priority(PENDING_TREE).distance_to_visible_in_pixels != 0)
+      continue;
+
     // If the missing region doesn't cover it, this tile is fully
     // covered by acceptable tiles at other scales.
-    if (!*iter || !missing_region.Intersects(iter.geometry_rect()))
+    if (!missing_region.Intersects(iter.geometry_rect()))
       continue;
-    iter->mark_required_for_activation();
 
-    // These must be true for this tile to end up in the NOW_BIN in TileManager.
-    DCHECK_EQ(iter->priority(PENDING_TREE).distance_to_visible_in_pixels, 0);
-    DCHECK_EQ(iter->priority(PENDING_TREE).time_to_visible_in_seconds, 0);
+    iter->mark_required_for_activation();
   }
 }
 
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index 0695ba1..499574b 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -825,6 +825,71 @@ TEST_F(PictureLayerImplTest, MarkRequiredNullTiles) {
   // It should be safe to call this (and MarkVisibleResourcesAsRequired)
   // on a layer with no recordings.
   host_impl_.pending_tree()->UpdateDrawProperties();
+  pending_layer_->MarkVisibleResourcesAsRequired();
+}
+
+TEST_F(PictureLayerImplTest, MarkRequiredOffscreenTiles) {
+  gfx::Size tile_size(100, 100);
+  gfx::Size layer_bounds(200, 100);
+
+  scoped_refptr<FakePicturePileImpl> pending_pile =
+      FakePicturePileImpl::CreateFilledPile(tile_size, layer_bounds);
+  SetupPendingTree(pending_pile);
+
+  pending_layer_->set_fixed_tile_size(tile_size);
+  ASSERT_TRUE(pending_layer_->CanHaveTilings());
+  PictureLayerTiling* tiling = pending_layer_->AddTiling(1.f);
+  host_impl_.pending_tree()->UpdateDrawProperties();
+  EXPECT_EQ(tiling->resolution(), HIGH_RESOLUTION);
+
+  // Fake set priorities.
+  int tile_count = 0;
+  for (PictureLayerTiling::CoverageIterator iter(
+           tiling,
+           pending_layer_->contents_scale_x(),
+           gfx::Rect(pending_layer_->visible_content_rect()));
+       iter;
+       ++iter) {
+    if (!*iter)
+      continue;
+    Tile* tile = *iter;
+    TilePriority priority;
+    priority.resolution = HIGH_RESOLUTION;
+    if (++tile_count % 2) {
+      priority.time_to_visible_in_seconds = 0.f;
+      priority.distance_to_visible_in_pixels = 0.f;
+    } else {
+      priority.time_to_visible_in_seconds = 1.f;
+      priority.distance_to_visible_in_pixels = 1.f;
+    }
+    tile->SetPriority(PENDING_TREE, priority);
+  }
+
+  pending_layer_->MarkVisibleResourcesAsRequired();
+
+  int num_visible = 0;
+  int num_offscreen = 0;
+
+  for (PictureLayerTiling::CoverageIterator iter(
+           tiling,
+           pending_layer_->contents_scale_x(),
+           gfx::Rect(pending_layer_->visible_content_rect()));
+       iter;
+       ++iter) {
+    if (!*iter)
+      continue;
+    const Tile* tile = *iter;
+    if (tile->priority(PENDING_TREE).distance_to_visible_in_pixels == 0.f) {
+      EXPECT_TRUE(tile->required_for_activation());
+      num_visible++;
+    } else {
+      EXPECT_FALSE(tile->required_for_activation());
+      num_offscreen++;
+    }
+  }
+
+  EXPECT_GT(num_visible, 0);
+  EXPECT_GT(num_offscreen, 0);
 }
 
 }  // namespace
diff --git a/cc/test/fake_picture_layer_impl.h b/cc/test/fake_picture_layer_impl.h
index 1efca43..c3d28f8 100644
--- a/cc/test/fake_picture_layer_impl.h
+++ b/cc/test/fake_picture_layer_impl.h
@@ -29,6 +29,7 @@ class FakePictureLayerImpl : public PictureLayerImpl {
   using PictureLayerImpl::AddTiling;
   using PictureLayerImpl::CleanUpTilingsOnActiveLayer;
   using PictureLayerImpl::CanHaveTilings;
+  using PictureLayerImpl::MarkVisibleResourcesAsRequired;
 
   PictureLayerImpl* twin_layer() { return twin_layer_; }
   PictureLayerTilingSet* tilings() { return tilings_.get(); }