Fix uninitialized offset

BUG=387783
R=palmer@chromium.org

Review URL: https://codereview.chromium.org/368783004

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 5e926c3..b9e5359 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -3078,7 +3078,7 @@
         }
         return pRet;
     }
-    FX_FILESIZE offset;
+    FX_FILESIZE offset = 0;
     FX_DWORD size = GetObjectSize(objnum, offset);
     size = (FX_DWORD)((FX_FILESIZE)(offset + size + 512) > m_dwFileLen ? m_dwFileLen - offset : size + 512);
     if (!m_pFileAvail->IsDataAvail(offset, size)) {