Update from https://crrev.com/304715

cc/resources/picture_layer_tiling_set.cc

 // Copyright 2012 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/picture_layer_tiling_set.h"
 
 #include <limits>
+#include <set>
 
 namespace cc {
 
 namespace {
 
 class LargestToSmallestScaleFunctor {
  public:
   bool operator() (PictureLayerTiling* left, PictureLayerTiling* right) {
     return left->contents_scale() > right->contents_scale();
   }
 };
 
+inline float LargerRatio(float float1, float float2) {
+  DCHECK_GT(float1, 0.f);
+  DCHECK_GT(float2, 0.f);
+  return float1 > float2 ? float1 / float2 : float2 / float1;
+}
+
 }  // namespace
 
 // static
 scoped_ptr<PictureLayerTilingSet> PictureLayerTilingSet::Create(
     PictureLayerTilingClient* client) {
   return make_scoped_ptr(new PictureLayerTilingSet(client));
 }
 
 PictureLayerTilingSet::PictureLayerTilingSet(PictureLayerTilingClient* client)
     : client_(client) {
 }
 
 PictureLayerTilingSet::~PictureLayerTilingSet() {
 }
 
 void PictureLayerTilingSet::SetClient(PictureLayerTilingClient* client) {
   client_ = client;
   for (size_t i = 0; i < tilings_.size(); ++i)
     tilings_[i]->SetClient(client_);
 }
 
 void PictureLayerTilingSet::RemoveTilesInRegion(const Region& region) {
   for (size_t i = 0; i < tilings_.size(); ++i)
     tilings_[i]->RemoveTilesInRegion(region);
 }
 
+void PictureLayerTilingSet::MarkAllTilingsNonIdeal() {
+  for (auto* tiling : tilings_)
+    tiling->set_resolution(NON_IDEAL_RESOLUTION);
+}
+
 bool PictureLayerTilingSet::SyncTilings(const PictureLayerTilingSet& other,
                                         const gfx::Size& new_layer_bounds,
                                         const Region& layer_invalidation,
                                         float minimum_contents_scale,
                                         RasterSource* raster_source) {
   if (new_layer_bounds.IsEmpty()) {
     RemoveAllTilings();
     return false;
   }
 
   tilings_.reserve(other.tilings_.size());
 
   // Remove any tilings that aren't in |other| or don't meet the minimum.
   for (size_t i = 0; i < tilings_.size(); ++i) {
     float scale = tilings_[i]->contents_scale();
-    if (scale >= minimum_contents_scale && !!other.TilingAtScale(scale))
+    if (scale >= minimum_contents_scale && !!other.FindTilingWithScale(scale))
       continue;
     // Swap with the last element and remove it.
     tilings_.swap(tilings_.begin() + i, tilings_.end() - 1);
     tilings_.pop_back();
     --i;
   }
 
   bool have_high_res_tiling = false;
 
   // Add any missing tilings from |other| that meet the minimum.
   for (size_t i = 0; i < other.tilings_.size(); ++i) {
     float contents_scale = other.tilings_[i]->contents_scale();
     if (contents_scale < minimum_contents_scale)
       continue;
-    if (PictureLayerTiling* this_tiling = TilingAtScale(contents_scale)) {
+    if (PictureLayerTiling* this_tiling = FindTilingWithScale(contents_scale)) {
       this_tiling->set_resolution(other.tilings_[i]->resolution());
 
       this_tiling->UpdateTilesToCurrentRasterSource(
           raster_source, layer_invalidation, new_layer_bounds);
       this_tiling->CreateMissingTilesInLiveTilesRect();
       if (this_tiling->resolution() == HIGH_RESOLUTION)
         have_high_res_tiling = true;
 
       DCHECK(this_tiling->tile_size() ==
              client_->CalculateTileSize(this_tiling->tiling_size()))
@@ skipping 33 matching lines @@
 
 int PictureLayerTilingSet::NumHighResTilings() const {
   int num_high_res = 0;
   for (size_t i = 0; i < tilings_.size(); ++i) {
     if (tilings_[i]->resolution() == HIGH_RESOLUTION)
       num_high_res++;
   }
   return num_high_res;
 }
 
-PictureLayerTiling* PictureLayerTilingSet::TilingAtScale(float scale) const {
+PictureLayerTiling* PictureLayerTilingSet::FindTilingWithScale(
+    float scale) const {
   for (size_t i = 0; i < tilings_.size(); ++i) {
     if (tilings_[i]->contents_scale() == scale)
       return tilings_[i];
   }
   return NULL;
 }
 
+PictureLayerTiling* PictureLayerTilingSet::FindTilingWithResolution(
+    TileResolution resolution) const {
+  auto iter = std::find_if(tilings_.begin(), tilings_.end(),
+                           [resolution](const PictureLayerTiling* tiling) {
+    return tiling->resolution() == resolution;
+  });
+  if (iter == tilings_.end())
+    return NULL;
+  return *iter;
+}
+
 void PictureLayerTilingSet::RemoveAllTilings() {
   tilings_.clear();
 }
 
 void PictureLayerTilingSet::Remove(PictureLayerTiling* tiling) {
   ScopedPtrVector<PictureLayerTiling>::iterator iter =
     std::find(tilings_.begin(), tilings_.end(), tiling);
   if (iter == tilings_.end())
     return;
   tilings_.erase(iter);
 }
 
+void PictureLayerTilingSet::RemoveTilingWithScale(float scale) {
+  auto iter = std::find_if(tilings_.begin(), tilings_.end(),
+                           [scale](const PictureLayerTiling* tiling) {
+    return tiling->contents_scale() == scale;
+  });
+  if (iter == tilings_.end())
+    return;
+  tilings_.erase(iter);
+}
+
 void PictureLayerTilingSet::RemoveAllTiles() {
   for (size_t i = 0; i < tilings_.size(); ++i)
     tilings_[i]->Reset();
 }
 
+float PictureLayerTilingSet::GetSnappedContentsScale(
+    float start_scale,
+    float snap_to_existing_tiling_ratio) const {
+  // If a tiling exists within the max snapping ratio, snap to its scale.
+  float snapped_contents_scale = start_scale;
+  float snapped_ratio = snap_to_existing_tiling_ratio;
+  for (const auto* tiling : tilings_) {
+    float tiling_contents_scale = tiling->contents_scale();
+    float ratio = LargerRatio(tiling_contents_scale, start_scale);
+    if (ratio < snapped_ratio) {
+      snapped_contents_scale = tiling_contents_scale;
+      snapped_ratio = ratio;
+    }
+  }
+  return snapped_contents_scale;
+}
+
+float PictureLayerTilingSet::GetMaximumContentsScale() const {
+  if (tilings_.empty())
+    return 0.f;
+  // The first tiling has the largest contents scale.
+  return tilings_[0]->contents_scale();
+}
+
 bool PictureLayerTilingSet::UpdateTilePriorities(
     const gfx::Rect& required_rect_in_layer_space,
     float ideal_contents_scale,
     double current_frame_time_in_seconds,
     const Occlusion& occlusion_in_layer_space,
     bool can_require_tiles_for_activation) {
   bool tiling_needs_update = false;
   // TODO(vmpstr): Check if we have to early out here, or if we can just do it
   // as part of computing tile priority rects for tilings.
   for (auto* tiling : tilings_) {
     if (tiling->NeedsUpdateForFrameAtTimeAndViewport(
             current_frame_time_in_seconds, required_rect_in_layer_space)) {
       tiling_needs_update = true;
       break;
     }
   }
   if (!tiling_needs_update)
     return false;
 
   for (auto* tiling : tilings_) {
     tiling->set_can_require_tiles_for_activation(
         can_require_tiles_for_activation);
     tiling->ComputeTilePriorityRects(
         required_rect_in_layer_space, ideal_contents_scale,
         current_frame_time_in_seconds, occlusion_in_layer_space);
   }
   return true;
 }
 
+void PictureLayerTilingSet::GetAllTilesForTracing(
+    std::set<const Tile*>* tiles) const {
+  for (auto* tiling : tilings_)
+    tiling->GetAllTilesForTracing(tiles);
+}
+
 PictureLayerTilingSet::CoverageIterator::CoverageIterator(
     const PictureLayerTilingSet* set,
     float contents_scale,
     const gfx::Rect& content_rect,
     float ideal_contents_scale)
     : set_(set),
       contents_scale_(contents_scale),
       ideal_contents_scale_(ideal_contents_scale),
       current_tiling_(-1) {
   missing_region_.Union(content_rect);
@@ skipping 207 matching lines @@
     case LOWER_THAN_LOW_RES:
       range = TilingRange(low_res_range.end, tilings_.size());
       break;
   }
 
   DCHECK_LE(range.start, range.end);
   return range;
 }
 
 }  // namespace cc