Fixup various overflow conditions

core/fxcrt/include/fx_coordinates.h

Index: core/fxcrt/include/fx_coordinates.h
diff --git a/core/fxcrt/include/fx_coordinates.h b/core/fxcrt/include/fx_coordinates.h
index eff2a7258a2bd5ca37315894b3d0f1072a5be482..75b1c472191e4a8fe9805b4b8d37f084be481649 100644
--- a/core/fxcrt/include/fx_coordinates.h
+++ b/core/fxcrt/include/fx_coordinates.h
@@ -150,6 +150,20 @@ struct FX_RECT {
   int Height() const { return bottom - top; }
   bool IsEmpty() const { return right <= left || bottom <= top; }
 
+  bool Valid() const {
+    pdfium::base::CheckedNumeric<int> w = right;

[Tom Sepez, 2016/08/08 21:09:45]

nit: I might write this as

pdfium::base::CheckedNumeric<int> w = right;
pdfium::base::CheckedNumeric<int> h = bottom;
w -= left;
h -= top;
return w.IsValid() && h.IsValid();

No sense optimizing for the invalid case.

[dsinclair, 2016/08/09 13:35:19]

Done.

+    w -= left;
+    if (!w.IsValid())
+      return false;
+
+    pdfium::base::CheckedNumeric<int> h = bottom;
+    h -= top;
+    if (!h.IsValid())
+      return false;
+
+    return true;
+  }
+
   void Normalize();
 
   void Intersect(const FX_RECT& src);