Fix int conversion warning

src/gpu/gl/debug/GrBufferObj.h

Index: src/gpu/gl/debug/GrBufferObj.h
diff --git a/src/gpu/gl/debug/GrBufferObj.h b/src/gpu/gl/debug/GrBufferObj.h
index 05d3cfddde04a33a91a59eb1f46bf740cfc49daa..5c282eef31ba931bfd9e30de16bf52a5b5a897ec 100644
--- a/src/gpu/gl/debug/GrBufferObj.h
+++ b/src/gpu/gl/debug/GrBufferObj.h
@@ -41,8 +41,8 @@ public:
     }
     void resetMapped()           { fMapped = false; }
     bool getMapped() const       { return fMapped; }
-    GrGLsizei getMappedOffset() const { return fMappedOffset; }
-    GrGLsizei getMappedLength() const { return fMappedLength; }
+    GrGLintptr getMappedOffset() const { return fMappedOffset; }
+    GrGLsizeiptr getMappedLength() const { return fMappedLength; }
 
     void setBound()              { fBound = true; }
     void resetBound()            { fBound = false; }