Fix uninitialized triangle

BUG=387835
R=palmer@chromium.org

Review URL: https://codereview.chromium.org/381173002

core/src/fpdfapi/fpdf_render/fpdf_render_pattern.cpp

diff --git a/core/src/fpdfapi/fpdf_render/fpdf_render_pattern.cpp b/core/src/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
index 0bf6311..926ce88 100644
--- a/core/src/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
+++ b/core/src/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
@@ -389,6 +389,8 @@
         return;
     }
     CPDF_MeshVertex triangle[3];
+    FXSYS_memset32(triangle, 0, sizeof(triangle));
+
     while (!stream.m_BitStream.IsEOF()) {
         CPDF_MeshVertex vertex;
         FX_DWORD flag = stream.GetVertex(vertex, pObject2Bitmap);