Make "priv" classes for GrTexure and GrSurface.

R=robertphillips@google.com, egdaniel@google.com, joshualitt@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/596053002
diff --git a/src/gpu/GrTextStrike.cpp b/src/gpu/GrTextStrike.cpp
index fa97f73..8ae10cc 100644
--- a/src/gpu/GrTextStrike.cpp
+++ b/src/gpu/GrTextStrike.cpp
@@ -7,6 +7,7 @@
 
 #include "GrGpu.h"
 #include "GrRectanizer.h"
+#include "GrSurfacePriv.h"
 #include "GrTextStrike.h"
 #include "GrTextStrike_impl.h"
 #include "SkString.h"
@@ -206,7 +207,7 @@
 #else
                 filename.printf("fontcache_%d%d.png", gDumpCount, i);
 #endif
-                texture->savePixels(filename.c_str());
+                texture->surfacePriv().savePixels(filename.c_str());
             }
         }
     }