Add over allocated memory of fixed array sub types to fixed array type.

The over allocated memory of fixed array type didn't equal to the sum of all
fixed array sub types previously, this patch adds over allocated memory of fixed
array sub types to fixed array type when we record fixed array sub type stats.

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2410083003
Cr-Commit-Position: refs/heads/master@{#40234}

src/heap/object-stats.h

@@ -75,6 +75,9 @@ class ObjectStats {
           over_allocated;
       over_allocated_histogram_[FIRST_FIXED_ARRAY_SUB_TYPE + array_sub_type]
                                [HistogramIndexFromSize(over_allocated)]++;
+      over_allocated_[InstanceType::FIXED_ARRAY_TYPE] += over_allocated;
+      over_allocated_histogram_[InstanceType::FIXED_ARRAY_TYPE]
+                               [HistogramIndexFromSize(over_allocated)]++;
     }
     return true;
   }