cc: Move LayerEvictionTileIterator to a separate file and make it a queue

cc/resources/tiling_set_eviction_queue.cc

Index: cc/resources/tiling_set_eviction_queue.cc
diff --git a/cc/resources/tiling_set_eviction_queue.cc b/cc/resources/tiling_set_eviction_queue.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8c5ff52f127099626c584429508b404d4ffce5e1
--- /dev/null
+++ b/cc/resources/tiling_set_eviction_queue.cc
@@ -0,0 +1,197 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/resources/tiling_set_eviction_queue.h"
+
+namespace cc {
+
+TilingSetEvictionQueue::TilingSetEvictionQueue()
+    : tiling_set_(nullptr),
+      tree_priority_(SAME_PRIORITY_FOR_BOTH_TREES),
+      current_category_(PictureLayerTiling::EVENTUALLY),
+      current_tiling_index_(0u),
+      current_tiling_range_type_(PictureLayerTilingSet::HIGHER_THAN_HIGH_RES),
+      current_eviction_tile_(nullptr),
+      eviction_tiles_(nullptr),
+      next_eviction_tile_index_(0u) {
+}
+
+TilingSetEvictionQueue::TilingSetEvictionQueue(
+    PictureLayerTilingSet* tiling_set,
+    TreePriority tree_priority)
+    : tiling_set_(tiling_set),
+      tree_priority_(tree_priority),
+      current_category_(PictureLayerTiling::EVENTUALLY),
+      current_tiling_index_(0u),
+      current_tiling_range_type_(PictureLayerTilingSet::HIGHER_THAN_HIGH_RES),
+      current_eviction_tile_(nullptr),
+      eviction_tiles_(nullptr),
+      next_eviction_tile_index_(0u) {
+  DCHECK(tiling_set_);
+
+  // Early out if the layer has no tilings.
+  if (!tiling_set_->num_tilings())
+    return;
+
+  current_tiling_index_ = CurrentTilingRange().start - 1u;
+  AdvanceToNextValidTiling();
+}
+
+TilingSetEvictionQueue::~TilingSetEvictionQueue() {
+}
+
+bool TilingSetEvictionQueue::IsEmpty() const {
+  return !current_eviction_tile_;
+}
+
+void TilingSetEvictionQueue::Pop() {
+  DCHECK(!IsEmpty());
+
+  if (!AdvanceToNextEvictionTile())
+    AdvanceToNextValidTiling();
+}
+
+Tile* TilingSetEvictionQueue::Top() {
+  DCHECK(!IsEmpty());
+  return current_eviction_tile_;
+}
+
+const Tile* TilingSetEvictionQueue::Top() const {
+  DCHECK(!IsEmpty());
+  return current_eviction_tile_;
+}
+
+bool TilingSetEvictionQueue::AdvanceToNextCategory() {
+  // Advance to the next category. This is done only after all tiling range
+  // types within the previous category have been gone through.
+  DCHECK_EQ(current_tiling_range_type_, PictureLayerTilingSet::HIGH_RES);
+
+  switch (current_category_) {
+    case PictureLayerTiling::EVENTUALLY:
+      current_category_ =
+          PictureLayerTiling::EVENTUALLY_AND_REQUIRED_FOR_ACTIVATION;
+      return true;
+    case PictureLayerTiling::EVENTUALLY_AND_REQUIRED_FOR_ACTIVATION:
+      current_category_ = PictureLayerTiling::SOON;
+      return true;
+    case PictureLayerTiling::SOON:
+      current_category_ = PictureLayerTiling::SOON_AND_REQUIRED_FOR_ACTIVATION;
+      return true;
+    case PictureLayerTiling::SOON_AND_REQUIRED_FOR_ACTIVATION:
+      current_category_ = PictureLayerTiling::NOW;
+      return true;
+    case PictureLayerTiling::NOW:
+      current_category_ = PictureLayerTiling::NOW_AND_REQUIRED_FOR_ACTIVATION;
+      return true;
+    case PictureLayerTiling::NOW_AND_REQUIRED_FOR_ACTIVATION:
+      return false;
+  }
+  NOTREACHED();
+  return false;
+}
+
+bool TilingSetEvictionQueue::AdvanceToNextEvictionTile() {
+  // Advance to the next eviction tile within the current category and tiling.
+  // This is done while advancing to a new tiling (in which case the next
+  // eviction tile index is 0) and while popping the current tile (in which
+  // case the next eviction tile index is greater than 0).
+  DCHECK_EQ(next_eviction_tile_index_ > 0, current_eviction_tile_ != nullptr);
+
+  while (next_eviction_tile_index_ < eviction_tiles_->size()) {
+    Tile* tile = (*eviction_tiles_)[next_eviction_tile_index_];
+    ++next_eviction_tile_index_;
+    if (tile->HasResources()) {
+      current_eviction_tile_ = tile;
+      return true;
+    }
+  }
+
+  current_eviction_tile_ = nullptr;
+  return false;
+}
+
+bool TilingSetEvictionQueue::AdvanceToNextTilingRangeType() {
+  // Advance to the next tiling range type within the current category or to
+  // the first tiling range type within the next category. This is done only
+  // after all tilings within the previous tiling range type have been gone
+  // through.
+  DCHECK_EQ(current_tiling_index_, CurrentTilingRange().end);
+
+  switch (current_tiling_range_type_) {
+    case PictureLayerTilingSet::HIGHER_THAN_HIGH_RES:
+      current_tiling_range_type_ = PictureLayerTilingSet::LOWER_THAN_LOW_RES;
+      return true;
+    case PictureLayerTilingSet::LOWER_THAN_LOW_RES:
+      current_tiling_range_type_ =
+          PictureLayerTilingSet::BETWEEN_HIGH_AND_LOW_RES;
+      return true;
+    case PictureLayerTilingSet::BETWEEN_HIGH_AND_LOW_RES:
+      current_tiling_range_type_ = PictureLayerTilingSet::LOW_RES;
+      return true;
+    case PictureLayerTilingSet::LOW_RES:
+      current_tiling_range_type_ = PictureLayerTilingSet::HIGH_RES;
+      return true;
+    case PictureLayerTilingSet::HIGH_RES:
+      if (!AdvanceToNextCategory())
+        return false;
+
+      current_tiling_range_type_ = PictureLayerTilingSet::HIGHER_THAN_HIGH_RES;
+      return true;
+  }
+  NOTREACHED();
+  return false;
+}
+
+bool TilingSetEvictionQueue::AdvanceToNextValidTiling() {
+  // Advance to the next tiling within current tiling range type or to
+  // the first tiling within the next tiling range type or category until
+  // the next eviction tile is found. This is done only after all eviction
+  // tiles within the previous tiling within the current category and tiling
+  // range type have been gone through.
+  DCHECK(!current_eviction_tile_);
+  DCHECK_NE(current_tiling_index_, CurrentTilingRange().end);
+
+  for (;;) {
+    ++current_tiling_index_;
+    while (current_tiling_index_ == CurrentTilingRange().end) {
+      if (!AdvanceToNextTilingRangeType())
+        return false;
+      current_tiling_index_ = CurrentTilingRange().start;
+    }
+
+    PictureLayerTiling* tiling = tiling_set_->tiling_at(CurrentTilingIndex());
+    eviction_tiles_ =
+        tiling->GetEvictionTiles(tree_priority_, current_category_);
+    next_eviction_tile_index_ = 0u;
+    if (AdvanceToNextEvictionTile())
+      return true;
+  }
+}
+
+PictureLayerTilingSet::TilingRange
+TilingSetEvictionQueue::CurrentTilingRange() const {
+  return tiling_set_->GetTilingRange(current_tiling_range_type_);
+}
+
+size_t TilingSetEvictionQueue::CurrentTilingIndex() const {
+  DCHECK_NE(current_tiling_index_, CurrentTilingRange().end);
+  switch (current_tiling_range_type_) {
+    case PictureLayerTilingSet::HIGHER_THAN_HIGH_RES:
+    case PictureLayerTilingSet::LOW_RES:
+    case PictureLayerTilingSet::HIGH_RES:
+      return current_tiling_index_;
+    // Tilings in the following ranges are accessed in reverse order.
+    case PictureLayerTilingSet::BETWEEN_HIGH_AND_LOW_RES:
+    case PictureLayerTilingSet::LOWER_THAN_LOW_RES: {
+      PictureLayerTilingSet::TilingRange tiling_range = CurrentTilingRange();
+      size_t current_tiling_range_offset =
+          current_tiling_index_ - tiling_range.start;
+      return tiling_range.end - 1 - current_tiling_range_offset;
+    }
+  }
+  NOTREACHED();
+  return 0;
+}
+
+}