Raster PictureLayerTiling with fractional translation

cc/tiles/picture_layer_tiling.h

Index: cc/tiles/picture_layer_tiling.h
diff --git a/cc/tiles/picture_layer_tiling.h b/cc/tiles/picture_layer_tiling.h
index b718ca1882a0839b66c99f870912c8c6be51aa7f..116baf5eec9476714d28013b38a5b4f2b6dcbd76 100644
--- a/cc/tiles/picture_layer_tiling.h
+++ b/cc/tiles/picture_layer_tiling.h
@@ -16,6 +16,7 @@
 
 #include "base/macros.h"
 #include "cc/base/region.h"
+#include "cc/base/scale_translate2d.h"
 #include "cc/base/tiling_data.h"
 #include "cc/cc_export.h"
 #include "cc/tiles/tile.h"
@@ -81,7 +82,7 @@ class CC_EXPORT PictureLayerTiling {
   static const int kBorderTexels = 1;
 
   PictureLayerTiling(WhichTree tree,
-                     float raster_scale,
+                     const ScaleTranslate2d& raster_transform,
                      scoped_refptr<RasterSource> raster_source,
                      PictureLayerTilingClient* client,
                      float min_preraster_distance,
@@ -120,7 +121,8 @@ class CC_EXPORT PictureLayerTiling {
   gfx::Size tiling_size() const { return tiling_data_.tiling_size(); }
   gfx::Rect live_tiles_rect() const { return live_tiles_rect_; }
   gfx::Size tile_size() const { return tiling_data_.max_texture_size(); }
-  float contents_scale() const { return contents_scale_; }
+  float contents_scale_key() const { return raster_transform_.scale(); }
+  const ScaleTranslate2d& raster_transform() const { return raster_transform_; }
   const TilingData* tiling_data() const { return &tiling_data_; }
 
   Tile* TileAt(int i, int j) const {
@@ -169,7 +171,7 @@ class CC_EXPORT PictureLayerTiling {
 
   void SetAllTilesOccludedForTesting() {
     gfx::Rect viewport_in_layer_space =
-        ScaleToEnclosingRect(current_visible_rect_, 1.f / contents_scale_);
+        EnclosingLayerRectFromContentsRect(current_visible_rect_);
     current_occlusion_in_layer_space_ =
         Occlusion(gfx::Transform(),
                   SimpleEnclosedRegion(viewport_in_layer_space),
@@ -220,7 +222,7 @@ class CC_EXPORT PictureLayerTiling {
     const PictureLayerTiling* tiling_ = nullptr;
     gfx::Size coverage_rect_max_bounds_;
     gfx::Rect coverage_rect_;
-    float coverage_to_content_scale_;
+    ScaleTranslate2d coverage_to_content_;
 
     Tile* current_tile_ = nullptr;
     gfx::Rect current_geometry_rect_;
@@ -330,8 +332,13 @@ class CC_EXPORT PictureLayerTiling {
   }
   void RemoveTilesInRegion(const Region& layer_region, bool recreate_tiles);
 
+  gfx::Rect EnclosingContentsRectFromLayerRect(
+      const gfx::Rect& layer_rect) const;
+  gfx::Rect EnclosingLayerRectFromContentsRect(
+      const gfx::Rect& contents_rect) const;
+
   // Given properties.
-  const float contents_scale_;
+  const ScaleTranslate2d raster_transform_;
   PictureLayerTilingClient* const client_;
   const WhichTree tree_;
   scoped_refptr<RasterSource> raster_source_;
@@ -353,7 +360,7 @@ class CC_EXPORT PictureLayerTiling {
   gfx::Rect current_soon_border_rect_;
   gfx::Rect current_eventually_rect_;
   // Other properties used for tile iteration and prioritization.
-  float current_content_to_screen_scale_;
+  float current_content_to_screen_scale_ = 0.f;
   Occlusion current_occlusion_in_layer_space_;
   float max_skewport_extent_in_screen_space_ = 0.f;