7016998: gcutil class LinearLeastSquareFit doesn't initialize some of its fields

Summary: Initialize _sum_x_squared, _intercept and _slope in constructor.
Reviewed-by: bobv, coleenp

src/share/vm/gc_implementation/shared/gcUtil.cpp

@@ -106,8 +106,8 @@ void AdaptivePaddedNoZeroDevAverage::sample(float new_sample) {
 }
 
 LinearLeastSquareFit::LinearLeastSquareFit(unsigned weight) :
-  _sum_x(0), _sum_y(0), _sum_xy(0),
-  _mean_x(weight), _mean_y(weight) {}
+  _sum_x(0), _sum_x_squared(0), _sum_y(0), _sum_xy(0),
+  _intercept(0), _slope(0), _mean_x(weight), _mean_y(weight) {}
 
 void LinearLeastSquareFit::update(double x, double y) {
   _sum_x = _sum_x + x;