Add path utils, plus a test for it.

SkOSFile:
Added class SkOSPath with functions for
modifying strings representing path names.

OSPathTest.cpp:
Test of the new utilities.

factory.cpp:
Use SkPathJoin.

gmmain and gm_expectations:
Use SkOSPath::SkPathJoin instead of a local version.

skimage_main.cpp:
Use the new location of SkPathJoin and SkBasename.

R=epoger@google.com

Review URL: https://codereview.chromium.org/15747004

git-svn-id: http://skia.googlecode.com/svn/trunk@9277 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index 3481cf8..3c4f27d 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -222,7 +222,7 @@
         filename.append(renderModeDescriptor);
         filename.appendUnichar('.');
         filename.append(suffix);
-        return SkPathJoin(path, filename.c_str());
+        return SkOSPath::SkPathJoin(path, filename.c_str());
     }
 
     /* since PNG insists on unpremultiplying our alpha, we take no