Add skstd::unique_ptr and use it.

include/gpu/gl/GrGLExtensions.h

Index: include/gpu/gl/GrGLExtensions.h
diff --git a/include/gpu/gl/GrGLExtensions.h b/include/gpu/gl/GrGLExtensions.h
index 6a8557b81a0b9fa7c1b3eeb97896fb19618f3668..96c5ed122270af38d9b675f6573bf7029b9a987e 100644
--- a/include/gpu/gl/GrGLExtensions.h
+++ b/include/gpu/gl/GrGLExtensions.h
@@ -28,7 +28,7 @@ public:
     GrGLExtensions& operator=(const GrGLExtensions&);
 
     void swap(GrGLExtensions* that) {
-        fStrings.swap(&that->fStrings);
+        fStrings.swap(that->fStrings);
         SkTSwap(fInitialized, that->fInitialized);
     }