Move headers used by headers in include/ to include/private.

include/gpu/gl/SkGLContext.h

Index: include/gpu/gl/SkGLContext.h
diff --git a/include/gpu/gl/SkGLContext.h b/include/gpu/gl/SkGLContext.h
index 3d232e558eebc6d2c8f7990db4e58e83fd4675f7..f9b32276e4285d006d30bc6df3ce5fcf1329b4c9 100644
--- a/include/gpu/gl/SkGLContext.h
+++ b/include/gpu/gl/SkGLContext.h
@@ -9,7 +9,7 @@
 #define SkGLContext_DEFINED
 
 #include "GrGLInterface.h"
-#include "../../src/gpu/SkGpuFenceSync.h"
+#include "../../private/SkGpuFenceSync.h"
 
 /**
  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
@@ -18,7 +18,7 @@
 
 class SK_API SkGLContext : public SkRefCnt {
 public:
-    
+
 
     ~SkGLContext() override;