cc: Remove tile sharing from tilings.

cc/resources/tiling_set_raster_queue_required.cc

Index: cc/resources/tiling_set_raster_queue_required.cc
diff --git a/cc/resources/tiling_set_raster_queue_required.cc b/cc/resources/tiling_set_raster_queue_required.cc
index 89ddb044255ed905ddcb963dffd62276e324305b..b44ee084879bd0b9d798b359c84f09b69f3502d7 100644
--- a/cc/resources/tiling_set_raster_queue_required.cc
+++ b/cc/resources/tiling_set_raster_queue_required.cc
@@ -19,19 +19,39 @@ TilingSetRasterQueueRequired::TilingSetRasterQueueRequired(
   DCHECK_NE(static_cast<int>(type),
             static_cast<int>(RasterTilePriorityQueue::Type::ALL));
 
-  // Any type of required tile would only come from a high resolution tiling.
-  // The functions that determine this value is
-  // PictureLayerTiling::IsTileRequiredFor*, which all return false if the
-  // resolution is not HIGH_RESOLUTION.
-  PictureLayerTiling* tiling =
-      tiling_set->FindTilingWithResolution(HIGH_RESOLUTION);
-  // If we don't have a high res tiling, then this queue will yield no tiles.
-  // See PictureLayerImpl::CanHaveTilings for examples of when a HIGH_RESOLUTION
+  // Required tiles should only come from HIGH_RESOLUTION tilings. However, if
+  // we want required for activation tiles on the active tree, then it will come
+  // from tilings whose pending twin is high resolution.
+  PictureLayerTiling* tiling = nullptr;
+  if (type == RasterTilePriorityQueue::Type::REQUIRED_FOR_ACTIVATION &&
+      tiling_set->client()->GetTree() == ACTIVE_TREE) {
+    for (size_t i = 0; i < tiling_set->num_tilings(); ++i) {
+      PictureLayerTiling* active_tiling = tiling_set->tiling_at(i);
+      const PictureLayerTiling* pending_twin =
+          tiling_set->client()->GetPendingOrActiveTwinTiling(active_tiling);
+      if (pending_twin && pending_twin->resolution() == HIGH_RESOLUTION) {
+        tiling = active_tiling;
+        break;
+      }
+    }
+  } else {
+    tiling = tiling_set->FindTilingWithResolution(HIGH_RESOLUTION);
+  }
+
+  // If we don't have a tiling, then this queue will yield no tiles. See
+  // PictureLayerImpl::CanHaveTilings for examples of when a HIGH_RESOLUTION
   // tiling would not be generated.
   if (!tiling)
     return;
 
-  iterator_ = TilingIterator(tiling, &tiling->tiling_data_);
+  if (type == RasterTilePriorityQueue::Type::REQUIRED_FOR_ACTIVATION) {
+    iterator_ = TilingIterator(tiling, &tiling->tiling_data_,
+                               tiling->pending_visible_rect());
+  } else {
+    iterator_ = TilingIterator(tiling, &tiling->tiling_data_,
+                               tiling->current_visible_rect());
+  }
+
   while (!iterator_.done() && !IsTileRequired(*iterator_))
     ++iterator_;
 }
@@ -73,19 +93,11 @@ TilingSetRasterQueueRequired::TilingIterator::TilingIterator()
 
 TilingSetRasterQueueRequired::TilingIterator::TilingIterator(
     PictureLayerTiling* tiling,
-    TilingData* tiling_data)
+    TilingData* tiling_data,
+    const gfx::Rect& rect)
     : tiling_(tiling), tiling_data_(tiling_data), current_tile_(nullptr) {
-  if (!tiling_->has_visible_rect_tiles()) {
-    // Verify that if we would create the iterator, then it would be empty (ie
-    // it would return false when evaluated as a bool).
-    DCHECK(!TilingData::Iterator(tiling_data_, tiling->current_visible_rect(),
-                                 false));
-    return;
-  }
-
   visible_iterator_ =
-      TilingData::Iterator(tiling_data_, tiling_->current_visible_rect(),
-                           false /* include_borders */);
+      TilingData::Iterator(tiling_data_, rect, false /* include_borders */);
   if (!visible_iterator_)
     return;