Fixing analyzer warnings on overloading == but not get hashCode.

tools/dom/templates/html/impl/impl_ClientRect.darttemplate

Index: tools/dom/templates/html/impl/impl_ClientRect.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_ClientRect.darttemplate b/tools/dom/templates/html/impl/impl_ClientRect.darttemplate
index 08d49b37ea3d734b0922f392d16748158ecb70c6..a7290fd315c4644308644dc52e6b562368bb153b 100644
--- a/tools/dom/templates/html/impl/impl_ClientRect.darttemplate
+++ b/tools/dom/templates/html/impl/impl_ClientRect.darttemplate
@@ -20,6 +20,9 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS implements Rect$IMPLEMENTS$NATIVESPEC {
         height == other.height;
   }
 
+  int get hashCode => JenkinsSmiHash.hash4(left.hashCode, top.hashCode,
+      width.hashCode, height.hashCode);
+
   /**
    * Computes the intersection of this rectangle and the rectangle parameter.
    * Returns null if there is no intersection.