Implement HiDPI and pinch-zoom scaling of filter params

cc/quads/render_pass_draw_quad.h

Index: cc/quads/render_pass_draw_quad.h
diff --git a/cc/quads/render_pass_draw_quad.h b/cc/quads/render_pass_draw_quad.h
index e3d6f14be8fca007ea36add050a59196fb46f064..08a3b271b4bad1461ed08a696109155bdc9cb13b 100644
--- a/cc/quads/render_pass_draw_quad.h
+++ b/cc/quads/render_pass_draw_quad.h
@@ -29,6 +29,7 @@ class CC_EXPORT RenderPassDrawQuad : public DrawQuad {
               const gfx::Rect& contents_changed_since_last_frame,
               const gfx::RectF& mask_uv_rect,
               const FilterOperations& filters,
+              const gfx::Vector2dF& filters_scale,
               const FilterOperations& background_filters);
 
   void SetAll(const SharedQuadState* shared_quad_state,
@@ -42,6 +43,7 @@ class CC_EXPORT RenderPassDrawQuad : public DrawQuad {
               const gfx::Rect& contents_changed_since_last_frame,
               const gfx::RectF& mask_uv_rect,
               const FilterOperations& filters,
+              const gfx::Vector2dF& filters_scale,
               const FilterOperations& background_filters);
 
   RenderPass::Id render_pass_id;
@@ -53,6 +55,13 @@ class CC_EXPORT RenderPassDrawQuad : public DrawQuad {
   // Post-processing filters, applied to the pixels in the render pass' texture.
   FilterOperations filters;
 
+  // The scale from layer space of the root layer of the render pass to
+  // the render pass physical pixels.
+  // This scale is applied to the filter parameters for pixel-moving filters.
+  // This scale should include content-to-target-space scale, and device
+  // pixel ratio.
+  gfx::Vector2dF filters_scale;
+
   // Post-processing filters, applied to the pixels showing through the
   // background of the render pass, from behind it.
   FilterOperations background_filters;