Add unit test for unbalanced save and restores in pictures.

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 284 matching lines @@
                        SaveFlags flags = kARGB_ClipLayer_SaveFlag);
 
     /** This call balances a previous call to save(), and is used to remove all
         modifications to the matrix/clip/drawFilter state since the last save
         call.
         It is an error to call restore() more times than save() was called.
     */
     virtual void restore();
 
     /** Returns the number of matrix/clip states on the SkCanvas' private stack.
-        This will equal # save() calls - # restore() calls.
+        This will equal # save() calls - # restore() calls + 1. The save count on
+        a new canvas is 1.
     */
     int getSaveCount() const;
 
     /** Efficient way to pop any calls to save() that happened after the save
-        count reached saveCount. It is an error for saveCount to be less than
-        getSaveCount()
+        count reached saveCount. It is an error for saveCount to be greater than
+        getSaveCount(). To pop all the way back to the initial matrix/clip context
+        pass saveCount == 1.
         @param saveCount    The number of save() levels to restore from
     */
     void restoreToCount(int saveCount);
 
     /** Returns true if drawing is currently going to a layer (from saveLayer)
      *  rather than to the root device.
      */
     virtual bool isDrawingToLayer() const;
 
     /** Preconcat the current matrix with the specified translation
@@ skipping 878 matching lines @@
             fCanvas->endCommentGroup();
         }
     }
 
 private:
     SkCanvas* fCanvas;
 };
 #define SkAutoCommentBlock(...) SK_REQUIRE_LOCAL_VAR(SkAutoCommentBlock)
 
 #endif