Scale the ALPHA_THRESHOLD filter's region based on the device scale factor.

cc/output/filter_operation.h

Index: cc/output/filter_operation.h
diff --git a/cc/output/filter_operation.h b/cc/output/filter_operation.h
index 626d2e7f06bb7e750c4ea9cd8cb2b309ec1b34ec..3de252f562fb8c4b5ca86b2ceee070ac8d6184af 100644
--- a/cc/output/filter_operation.h
+++ b/cc/output/filter_operation.h
@@ -89,6 +89,11 @@ class CC_EXPORT FilterOperation {
     return region_;
   }
 
+  float device_scale_factor() const {
+    DCHECK_EQ(type_, ALPHA_THRESHOLD);
+    return device_scale_factor_;
+  }
+
   static FilterOperation CreateGrayscaleFilter(float amount) {
     return FilterOperation(GRAYSCALE, amount);
   }
@@ -149,10 +154,14 @@ class CC_EXPORT FilterOperation {
   }
 
   static FilterOperation CreateAlphaThresholdFilter(const SkRegion& region,
+                                                    float device_scale_factor,

[danakj, 2014/06/17 21:35:28]

The fact that you're setting this to the DSF doesn't seem relevant to the
FilterOperation, it's just a scale that will be applied to the alpha filter.
Let's just call it a general "scale factor" in this code.

[garykac, 2014/07/10 23:02:24]

Acknowledged.

                                                     float inner_threshold,
                                                     float outer_threshold) {
-    return FilterOperation(ALPHA_THRESHOLD, region,
-                           inner_threshold, outer_threshold);
+    return FilterOperation(ALPHA_THRESHOLD,
+                           region,
+                           device_scale_factor,
+                           inner_threshold,
+                           outer_threshold);
   }
 
   bool operator==(const FilterOperation& other) const;
@@ -210,6 +219,11 @@ class CC_EXPORT FilterOperation {
     region_ = region;
   }
 
+  void set_device_scale_factor(float scale) {
+    DCHECK_EQ(type_, ALPHA_THRESHOLD);
+    device_scale_factor_ = scale;
+  }
+
   // Given two filters of the same type, returns a filter operation created by
   // linearly interpolating a |progress| fraction from |from| to |to|. If either
   // |from| or |to| (but not both) is null, it is treated as a no-op filter of
@@ -239,6 +253,7 @@ class CC_EXPORT FilterOperation {
 
   FilterOperation(FilterType type,
                   const SkRegion& region,
+                  float device_scale_factor,
                   float inner_threshold,
                   float outer_threshold);
 
@@ -251,6 +266,7 @@ class CC_EXPORT FilterOperation {
   SkScalar matrix_[20];
   int zoom_inset_;
   SkRegion region_;
+  float device_scale_factor_;
 };
 
 }  // namespace cc