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

cc/resources/tiling_set_raster_queue.cc

Index: cc/resources/tiling_set_raster_queue.cc
diff --git a/cc/resources/tiling_set_raster_queue.cc b/cc/resources/tiling_set_raster_queue.cc
new file mode 100644
index 0000000000000000000000000000000000000000..08f7642b8c55ed51921d49ccc462967f93971452
--- /dev/null
+++ b/cc/resources/tiling_set_raster_queue.cc
@@ -0,0 +1,117 @@
+// 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_raster_queue.h"
+
+namespace cc {
+
+TilingSetRasterQueue::TilingSetRasterQueue()
+    : tiling_set_(nullptr), current_stage_(arraysize(stages_)) {
+}
+
+TilingSetRasterQueue::TilingSetRasterQueue(PictureLayerTilingSet* tiling_set,
+                                           bool prioritize_low_res)
+    : tiling_set_(tiling_set), current_stage_(0) {
+  DCHECK(tiling_set_);
+
+  // Early out if the tiling set has no tilings.
+  if (!tiling_set_->num_tilings()) {
+    current_stage_ = arraysize(stages_);
+    return;
+  }
+
+  // Find high and low res tilings and initialize the iterators.
+  for (size_t i = 0; i < tiling_set_->num_tilings(); ++i) {
+    PictureLayerTiling* tiling = tiling_set_->tiling_at(i);
+    if (tiling->resolution() == HIGH_RESOLUTION) {
+      iterators_[HIGH_RES] =
+          PictureLayerTiling::TilingRasterTileIterator(tiling);
+    }
+
+    if (prioritize_low_res && tiling->resolution() == LOW_RESOLUTION) {
+      iterators_[LOW_RES] =
+          PictureLayerTiling::TilingRasterTileIterator(tiling);
+    }
+  }
+
+  if (prioritize_low_res) {
+    stages_[0].iterator_type = LOW_RES;
+    stages_[0].tile_type = TilePriority::NOW;
+
+    stages_[1].iterator_type = HIGH_RES;
+    stages_[1].tile_type = TilePriority::NOW;
+  } else {
+    stages_[0].iterator_type = HIGH_RES;
+    stages_[0].tile_type = TilePriority::NOW;
+
+    stages_[1].iterator_type = LOW_RES;
+    stages_[1].tile_type = TilePriority::NOW;
+  }
+
+  stages_[2].iterator_type = HIGH_RES;
+  stages_[2].tile_type = TilePriority::SOON;
+
+  stages_[3].iterator_type = HIGH_RES;
+  stages_[3].tile_type = TilePriority::EVENTUALLY;
+
+  IteratorType index = stages_[current_stage_].iterator_type;
+  TilePriority::PriorityBin tile_type = stages_[current_stage_].tile_type;
+  if (!iterators_[index] || iterators_[index].get_type() != tile_type)
+    AdvanceToNextStage();
+}
+
+TilingSetRasterQueue::~TilingSetRasterQueue() {
+}
+
+bool TilingSetRasterQueue::IsEmpty() const {
+  return current_stage_ >= arraysize(stages_);
+}
+
+void TilingSetRasterQueue::Pop() {
+  IteratorType index = stages_[current_stage_].iterator_type;
+  TilePriority::PriorityBin tile_type = stages_[current_stage_].tile_type;
+
+  // First advance the iterator.
+  DCHECK(iterators_[index]);
+  DCHECK(iterators_[index].get_type() == tile_type);
+  ++iterators_[index];
+
+  if (!iterators_[index] || iterators_[index].get_type() != tile_type)
+    AdvanceToNextStage();
+}
+
+Tile* TilingSetRasterQueue::Top() {
+  DCHECK(!IsEmpty());
+
+  IteratorType index = stages_[current_stage_].iterator_type;
+  DCHECK(iterators_[index]);
+  DCHECK(iterators_[index].get_type() == stages_[current_stage_].tile_type);
+
+  return *iterators_[index];
+}
+
+const Tile* TilingSetRasterQueue::Top() const {
+  DCHECK(!IsEmpty());
+
+  IteratorType index = stages_[current_stage_].iterator_type;
+  DCHECK(iterators_[index]);
+  DCHECK(iterators_[index].get_type() == stages_[current_stage_].tile_type);
+
+  return *iterators_[index];
+}
+
+void TilingSetRasterQueue::AdvanceToNextStage() {
+  DCHECK_LT(current_stage_, arraysize(stages_));
+  ++current_stage_;
+  while (current_stage_ < arraysize(stages_)) {
+    IteratorType index = stages_[current_stage_].iterator_type;
+    TilePriority::PriorityBin tile_type = stages_[current_stage_].tile_type;
+
+    if (iterators_[index] && iterators_[index].get_type() == tile_type)
+      break;
+    ++current_stage_;
+  }
+}
+
+}  // namespace cc