Factor code to rotate a canvas about a point.

tools/sk_tool_utils.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 sk_tool_utils_DEFINED
 #define sk_tool_utils_DEFINED
 
 #include "SkColor.h"
 #include "SkImageEncoder.h"
 #include "SkImageInfo.h"
 #include "SkPixelSerializer.h"
 #include "SkRandom.h"
 #include "SkTDArray.h"
 #include "SkTypeface.h"
 
 class SkBitmap;
 class SkCanvas;
 class SkPaint;
 class SkPath;
 class SkShader;
 class SkTestFont;
 class SkTextBlobBuilder;
 
 namespace sk_tool_utils {
 
+    /** Rotate the canvas around the given point. */
+    void rotate_about(SkCanvas* canvas, SkScalar degrees, SkScalar px, SkScalar py);
+
     const char* colortype_name(SkColorType);
 
     /**
      * Map opaque colors from 8888 to 565.
      */
     SkColor color_to_565(SkColor color);
 
     /**
      * Return a color emoji typeface if available.
      */
@@ skipping 177 matching lines @@
         int  fID;
         int  fOutputPos;
         bool fTempMark;
 
         SkTDArray<TopoTestNode*> fDependencies;
     };
 
 }  // namespace sk_tool_utils
 
 #endif  // sk_tool_utils_DEFINED