Added skslc parse recursion limit

src/sksl/SkSLParser.h

Index: src/sksl/SkSLParser.h
diff --git a/src/sksl/SkSLParser.h b/src/sksl/SkSLParser.h
index d1ae0d0e9f5d2f70883f751db151214322edf328..f9dcde244f5b20de3786af812a3ab035c78a8f9e 100644
--- a/src/sksl/SkSLParser.h
+++ b/src/sksl/SkSLParser.h
@@ -197,12 +197,16 @@ private:
 
     bool identifier(std::string* dest);
 
-
     void* fScanner;
     YY_BUFFER_STATE fBuffer;
+    // current parse depth, used to enforce a recursion limit to try to keep us from overflowing the
+    // stack on pathological inputs
+    int fDepth = 0;
     Token fPushback;
     SymbolTable& fTypes;
     ErrorReporter& fErrors;
+
+    friend class AutoDepth;
 };
 
 } // namespace