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

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.

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"
 

src/core/SkRecords.h

@@ -8,10 +8,10 @@
 #ifndef SkRecords_DEFINED
 #define SkRecords_DEFINED
 
+#include "../private/SkPathPriv.h"
 #include "SkCanvas.h"
 #include "SkDrawable.h"
 #include "SkMatrix.h"
-#include "SkPathPriv.h"
 #include "SkPicture.h"
 #include "SkRSXform.h"
 #include "SkTextBlob.h"