add header guards

Change-Id: I3680ea31bf279cc6bde58c15a3dfa6b49815cf7e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/225138
Auto-Submit: Hal Canary <halcanary@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/src/gpu/geometry/GrQuadBuffer.h b/src/gpu/geometry/GrQuadBuffer.h
index a2e2f4c..dbdc92c 100644
--- a/src/gpu/geometry/GrQuadBuffer.h
+++ b/src/gpu/geometry/GrQuadBuffer.h
@@ -4,6 +4,8 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+#ifndef GrQuadBuffer_DEFINED
+#define GrQuadBuffer_DEFINED
 
 #include "include/private/SkTDArray.h"
 #include "src/gpu/geometry/GrQuad.h"
@@ -373,3 +375,4 @@
     // Nothing else is needed to do but report whether or not the updated pointer is valid
     return fCurrentEntry < fBuffer->fData.end();
 }
+#endif  // GrQuadBuffer_DEFINED