[interpreter] A few code coverage improvements.

src/interpreter/constant-array-builder.cc

Index: src/interpreter/constant-array-builder.cc
diff --git a/src/interpreter/constant-array-builder.cc b/src/interpreter/constant-array-builder.cc
index dd3b2ac11fc2e34e49cf520404325d0ac60c2a1b..7ce50b580e998e0f170f6c8bd29eb237627f1ffd 100644
--- a/src/interpreter/constant-array-builder.cc
+++ b/src/interpreter/constant-array-builder.cc
@@ -59,7 +59,7 @@ ConstantArrayBuilder::ConstantArrayBuilder(Isolate* isolate, Zone* zone)
   idx_slice_[1] = new (zone) ConstantArraySlice(
       zone, k8BitCapacity, k16BitCapacity, OperandSize::kShort);
   idx_slice_[2] = new (zone) ConstantArraySlice(
-      zone, k16BitCapacity, k32BitCapacity, OperandSize::kQuad);
+      zone, k8BitCapacity + k16BitCapacity, k32BitCapacity, OperandSize::kQuad);

[mythria, 2016/04/01 10:10:42]

This also fixes a clusterfuzz bug.
https://bugs.chromium.org/p/chromium/issues/detail?id=599000 :). 

 }
 
 size_t ConstantArrayBuilder::size() const {