Have /src files use header directly.

BUG=skia:

Review URL: https://codereview.chromium.org/1373253003
diff --git a/src/core/SkString.cpp b/src/core/SkString.cpp
index af5fa7a..d93f662 100644
--- a/src/core/SkString.cpp
+++ b/src/core/SkString.cpp
@@ -7,7 +7,7 @@
  */
 
 
-#include "../private/SkAtomics.h"
+#include "SkAtomics.h"
 #include "SkFixed.h"
 #include "SkString.h"
 #include "SkUtils.h"