Fix code that left shifts a negative value. This has undefined behavior.

tests/ClampRangeTest.cpp

Index: tests/ClampRangeTest.cpp
diff --git a/tests/ClampRangeTest.cpp b/tests/ClampRangeTest.cpp
index ccce8c5bf3bc0286793b422275dd29207e7d2909..9027e9b31146323afd58e97f7b84529214b74c9c 100644
--- a/tests/ClampRangeTest.cpp
+++ b/tests/ClampRangeTest.cpp
@@ -82,8 +82,7 @@ DEF_TEST(ClampRange, reporter) {
     test_range(ff(1),  ff(16384),  100);
     test_range(ff(-1), ff(-16384), 100);
     test_range(ff(1)/2, ff(16384), 100);
-    // TODO(reed): skia:2481, fix whatever bug this is, then uncomment
-    //test_range(ff(1)/2, ff(-16384), 100);
+    test_range(ff(1)/2, ff(-16384), 100);
 
     SkRandom rand;