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/bench/SkipZeroesBench.cpp b/bench/SkipZeroesBench.cpp
index 30d9377..fc25f8b 100644
--- a/bench/SkipZeroesBench.cpp
+++ b/bench/SkipZeroesBench.cpp
@@ -52,8 +52,7 @@
             return;
         }
 
-        SkString fullPath = SkOSPath::SkPathJoin(resourcePath.c_str(),
-                                                 fFilename.c_str());
+        SkString fullPath = SkOSPath::Join(resourcePath.c_str(), fFilename.c_str());
         SkFILEStream fileStream(fullPath.c_str());
         fValid = fileStream.isValid() && fileStream.getLength() > 0;
         if (fValid) {