Add path utils, plus a test for it.

include/core/SkOSFile.h

Index: include/core/SkOSFile.h
diff --git a/include/core/SkOSFile.h b/include/core/SkOSFile.h
index 257b66ae67b30454d5819bcf21a15752bc378d9b..e67da3bfa9651a1787ce333b9d42b52423fe1557 100644
--- a/include/core/SkOSFile.h
+++ b/include/core/SkOSFile.h
@@ -105,4 +105,26 @@ private:
     uint16_t*   fStr;
 };
 
+/**
+ *  Functions for modifying SkStrings which represent paths on the filesystem.
+ */
+namespace SkOSPathUtils {
+    /**
+     * Assembles rootPath and relativePath into a single path, like this:
+     * rootPath/relativePath
+     *
+     * Uses SkPATH_SEPARATOR, to work on all platforms.
+     */
+    SkString SkPathJoin(const char *rootPath, const char *relativePath);

[epoger, 2013/05/24 16:42:55]

Rather than creating the new SkOSPathUtils namespace, maybe make these static
methods in a new SkOSPath class?  That seems more consistent with the SkOSFile
class defined above.

But I don't feel strongly about it.

[scroggo, 2013/05/24 17:36:05]

I like that better. Done.

+
+    /**
+     *  Return the name of the file, ignoring the directory structure.
+     *  Behaves like python's os.path.basename. If the fullPath is
+     *  /dir/subdir/, an empty string is returned.
+     *  @param fullPath Full path to the file.
+     *  @return SkString The basename of the file - anything beyond the
+     *      final slash, or the full name if there is no slash.
+     */
+    SkString SkBasename(const char* fullPath);
+}
 #endif