Move headers with no dependencies.

C.f.  https://codereview.chromium.org/1261013003/

BUG=skia:4126

Will follow up with two more CLs if this works:
  - one moving SkRecords.h
  - one moving SkMiniRecorder.h

No public API changes.
TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/117842223bd13325b6da26110d80e0590c1a742b

Review URL: https://codereview.chromium.org/1266593002

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;
 

include/views/SkOSWindow_Win.h

@@ -10,7 +10,7 @@
 #ifndef SkOSWindow_Win_DEFINED
 #define SkOSWindow_Win_DEFINED
 
-#include "../../src/core/SkFunction.h"
+#include "../private/SkFunction.h"
 #include "../private/SkTHash.h"
 #include "SkWindow.h"