Add isEmpty() query to GrShape and improve comments.

src/gpu/GrShape.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrShape_DEFINED
 #define GrShape_DEFINED
 
@@ skipping 97 matching lines @@
 
     /**
      * Returns a shape that has either applied the path effect or path effect and stroking
      * information from this shape's style to its geometry. Scale is used when approximating the
      * output geometry and typically is computed from the view matrix
      */
     GrShape applyStyle(GrStyle::Apply apply, SkScalar scale) {
         return GrShape(*this, apply, scale);
     }
 
+    /** Returns the unstyled geometry as a rrect if possible. */
     bool asRRect(SkRRect* rrect) const {
         if (Type::kRRect != fType) {
             return false;
         }
         if (rrect) {
             *rrect = fRRect;
         }
         return true;
     }
 
+    /** Returns the unstyled geometry as a path. */
     void asPath(SkPath* out) const {
         switch (fType) {
             case Type::kEmpty:
                 out->reset();
                 break;
             case Type::kRRect:
                 out->reset();
                 out->addRRect(fRRect);
                 break;
             case Type::kPath:
                 *out = *fPath.get();
                 break;
         }
     }
 
     /**
-     * Is it known that the shape has no unclosed contours. This means that it will not have
-     * any caps if stroked (modulo the effect of any path effect).
+     * Returns whether the geometry is empty. Note that applying the style could produce a
+     * non-empty shape.
+     */
+    bool isEmpty() const { return Type::kEmpty == fType; }
+
+    /**
+     * Is it known that the unstyled geometry has no unclosed contours. This means that it will
+     * not have any caps if stroked (modulo the effect of any path effect).
      */
     bool knownToBeClosed() const {
         switch (fType) {
             case Type::kEmpty:
                 return true;
             case Type::kRRect:
                 return true;
             case Type::kPath:
                 return false;
         }
@@ skipping 72 matching lines @@
         return Type::kPath;
     }
 
     Type                        fType;
     SkRRect                     fRRect;
     SkTLazy<SkPath>             fPath;
     GrStyle                     fStyle;
     SkAutoSTArray<8, uint32_t>  fInheritedKey;
 };
 #endif