Reduce FM2JS parser depth limit to avoid memory exhaustion

The current limit of 2000 is still causing occassional ASAN issues,
reducing to 1250.

BUG=chromium:757711

Change-Id: Idb07f97b01230afabcceaa23b29495432193ec64
Reviewed-on: https://pdfium-review.googlesource.com/11750
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/xfa/fxfa/fm2js/cxfa_fmparser.cpp b/xfa/fxfa/fm2js/cxfa_fmparser.cpp
index 42a65e5..2981a4d 100644
--- a/xfa/fxfa/fm2js/cxfa_fmparser.cpp
+++ b/xfa/fxfa/fm2js/cxfa_fmparser.cpp
@@ -15,7 +15,7 @@
 namespace {
 
 const unsigned int kMaxAssignmentChainLength = 12;
-const unsigned int kMaxParseDepth = 2000;
+const unsigned int kMaxParseDepth = 1250;
 
 }  // namespace