Cleanup: Rename SkOSPath functions.

Mostly for brevity and matches better with Python:

Python           | Old C++                 | New C++
os.path.join     | SkOSPath::SkPathJoin    | SkOSPath::Join
os.path.basename | SkOSPath::SkBasename    | SkOSPath::Basename

BUG=None
TEST=make all
R=mtklein@google.com, bsalomon@google.com

Author: tfarina@chromium.org

Review URL: https://codereview.chromium.org/428443002
diff --git a/tools/PictureRenderer.cpp b/tools/PictureRenderer.cpp
index 3793b85..dd4cea4 100644
--- a/tools/PictureRenderer.cpp
+++ b/tools/PictureRenderer.cpp
@@ -363,7 +363,7 @@
     SkAutoTUnref<SkPicture> picture(recorder.endRecording());
     if (!fWritePath.isEmpty()) {
         // Record the new picture as a new SKP with PNG encoded bitmaps.
-        SkString skpPath = SkOSPath::SkPathJoin(fWritePath.c_str(), fInputFilename.c_str());
+        SkString skpPath = SkOSPath::Join(fWritePath.c_str(), fInputFilename.c_str());
         SkFILEWStream stream(skpPath.c_str());
         picture->serialize(&stream, &encode_bitmap_to_data);
         return true;