Have /src files use header directly.

BUG=skia:

Review URL: https://codereview.chromium.org/1373253003
diff --git a/src/core/SkClipStack.cpp b/src/core/SkClipStack.cpp
index 1fd621b..f54d57f 100644
--- a/src/core/SkClipStack.cpp
+++ b/src/core/SkClipStack.cpp
@@ -5,7 +5,7 @@
  * found in the LICENSE file.
  */
 
-#include "../private/SkAtomics.h"
+#include "SkAtomics.h"
 #include "SkCanvas.h"
 #include "SkClipStack.h"
 #include "SkPath.h"