Add some comments to GrRectanizer_skyline

src/gpu/GrRectanizer_skyline.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrRectanizer_skyline_DEFINED
 #define GrRectanizer_skyline_DEFINED
 
@@ skipping 14 matching lines @@
         fAreaSoFar = 0;
         fSkyline.reset();
         SkylineSegment* seg = fSkyline.append(1);
         seg->fX = 0;
         seg->fY = 0;
         seg->fWidth = this->width();
     }
 
     virtual bool addRect(int w, int h, SkIPoint16* loc) SK_OVERRIDE;
 
-    virtual float percentFull() const SK_OVERRIDE{
+    virtual float percentFull() const SK_OVERRIDE {
         return fAreaSoFar / ((float)this->width() * this->height());
     }
 
 private:
     struct SkylineSegment {
         int  fX;
         int  fY;
         int  fWidth;
     };
 
     SkTDArray<SkylineSegment> fSkyline;
 
     int32_t fAreaSoFar;
 
+    // Can a width x height rectangle fit in the free space represented by
+    // the skyline segments >= 'skylineIndex'? If so, return true and fill in
+    // 'y' with the y-location at which it fits (the x location is pulled from 
+    // 'skylineIndex's segment.
     bool rectangleFits(int skylineIndex, int width, int height, int* y) const;
+    // Update the skyline structure to include a width x height rect located
+    // at x,y.
     void addSkylineLevel(int skylineIndex, int x, int y, int width, int height);
 
     typedef GrRectanizer INHERITED;
 };
 
 #endif