Add option to dump images from nanobench.

include/core/SkOSFile.h

Index: include/core/SkOSFile.h
diff --git a/include/core/SkOSFile.h b/include/core/SkOSFile.h
index 39eeb4b0b09a94ae9984f5a31b9f0559ec984410..69a74dfcaa3331594a1ef68a9824c4eb700945e3 100644
--- a/include/core/SkOSFile.h
+++ b/include/core/SkOSFile.h
@@ -123,7 +123,7 @@ public:
 /**
  *  Functions for modifying SkStrings which represent paths on the filesystem.
  */
-class SkOSPath {
+class SkOSPath   {
 public:
     /**
      * Assembles rootPath and relativePath into a single path, like this:
@@ -144,6 +144,17 @@ public:
      *      final slash, or the full name if there is no slash.
      */
     static SkString Basename(const char* fullPath);
+
+    /**
+     *  Given a qualified file name returns the directory.
+     *  Behaves like python's os.path.dirname. If the fullPath is
+     *  /dir/subdir/ the return will be /dir/subdir/
+     *  @param fullPath Full path to the file.
+     *  @return SkString The dir containing the file - anything preceding the
+     *      final slash, or the full name if ending in a slash.
+     */
+    static SkString Dirname(const char* fullPath);
+    
 };
 
 #endif