|  | diff --git a/third_party/agg23/agg_vcgen_dash.cpp b/third_party/agg23/agg_vcgen_dash.cpp | 
|  | index f690760b0..d44fca178 100644 | 
|  | --- a/third_party/agg23/agg_vcgen_dash.cpp | 
|  | +++ b/third_party/agg23/agg_vcgen_dash.cpp | 
|  | @@ -18,8 +18,11 @@ | 
|  | // | 
|  | //---------------------------------------------------------------------------- | 
|  |  | 
|  | +#include <cmath> | 
|  | + | 
|  | #include "agg_shorten_path.h" | 
|  | #include "agg_vcgen_dash.h" | 
|  | +#include "core/fxcrt/check_op.h" | 
|  |  | 
|  | namespace pdfium | 
|  | { | 
|  | @@ -60,6 +63,8 @@ void vcgen_dash::dash_start(float ds) | 
|  | } | 
|  | void vcgen_dash::calc_dash_start(float ds) | 
|  | { | 
|  | +    DCHECK_GT(m_total_dash_len, 0); | 
|  | +    ds -= floor(ds / m_total_dash_len) * m_total_dash_len; | 
|  | m_curr_dash = 0; | 
|  | m_curr_dash_start = 0; | 
|  | while(ds > 0) { |