Update from https://crrev.com/304715

cc/resources/picture_layer_tiling_set.cc

Index: cc/resources/picture_layer_tiling_set.cc
diff --git a/cc/resources/picture_layer_tiling_set.cc b/cc/resources/picture_layer_tiling_set.cc
index 060bd27faf081d783381dc09aad68019d7253021..35170a0baf5e54665be05928bf9d26a51579a8e3 100644
--- a/cc/resources/picture_layer_tiling_set.cc
+++ b/cc/resources/picture_layer_tiling_set.cc
@@ -5,6 +5,7 @@
 #include "cc/resources/picture_layer_tiling_set.h"
 
 #include <limits>
+#include <set>
 
 namespace cc {
 
@@ -17,6 +18,12 @@ class LargestToSmallestScaleFunctor {
   }
 };
 
+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
@@ -43,6 +50,11 @@ void PictureLayerTilingSet::RemoveTilesInRegion(const Region& region) {
     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,
@@ -58,7 +70,7 @@ bool PictureLayerTilingSet::SyncTilings(const PictureLayerTilingSet& other,
   // 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);
@@ -73,7 +85,7 @@ bool PictureLayerTilingSet::SyncTilings(const PictureLayerTilingSet& other,
     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(
@@ -127,7 +139,8 @@ int PictureLayerTilingSet::NumHighResTilings() const {
   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];
@@ -135,6 +148,17 @@ PictureLayerTiling* PictureLayerTilingSet::TilingAtScale(float scale) const {
   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();
 }
@@ -147,11 +171,45 @@ void PictureLayerTilingSet::Remove(PictureLayerTiling* tiling) {
   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,
@@ -181,6 +239,12 @@ bool PictureLayerTilingSet::UpdateTilePriorities(
   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,