Fix memory leak in build example

site/user/sample/building.md

 Building with Skia Tutorial
 ===========================
 
 dsinclair@chromium.org
 
 
 This document describes the steps used to create an application that uses Skia.  The assumptions are that you're using:
 
   * [git](http://git-scm.com)
   * [gclient](https://code.google.com/p/gclient/)
@@ skipping 242 matching lines @@
 Our application is defined in `src/app/main.cpp` as:
 
 ~~~~
 #include "SkPaint.h"
 #include "SkString.h"
 
 int main(int argc, char** argv) {
   SkPaint paint;
   paint.setColor(SK_ColorRED);
 
-  SkString* str = new SkString();
-  paint.toString(str);
+  SkString str;
+  paint.toString(&str);
 
-  fprintf(stdout, "%s\n", str->c_str());
+  fprintf(stdout, "%s\n", str.c_str());
 
   return 0;
 }
 ~~~~
 
 We're just printing out an SkPaint to show that everything is linking correctly.
 
 Now, we can run:
 
     $ ./build/gyp_using_skia
@@ skipping 33 matching lines @@
       {
         # A change to a .gyp, .gypi or to GYP itself should run the generator.
         "name": "gyp",
         "pattern": ".",
         "action": ["python", "src/build/gyp_using_skia"]
       }
     ]
 
 Adding the above to the end of DEPS and running gclient sync should show the
 GYP files being updated at the end of the sync procedure.
-