cc: Update SpreadForStdDeviation to 3*sigma, and update tests.

cc/output/filter_operations_unittest.cc

Index: cc/output/filter_operations_unittest.cc
diff --git a/cc/output/filter_operations_unittest.cc b/cc/output/filter_operations_unittest.cc
index a866141858c6bdf4a3afb738a54757c5da91b39c..64c127c29f2891c032efc6be41fa6045b1f2da25 100644
--- a/cc/output/filter_operations_unittest.cc
+++ b/cc/output/filter_operations_unittest.cc
@@ -21,10 +21,10 @@ TEST(FilterOperationsTest, GetOutsetsBlur) {
   int top, right, bottom, left;
   top = right = bottom = left = 0;
   ops.GetOutsets(&top, &right, &bottom, &left);
-  EXPECT_EQ(57, top);
-  EXPECT_EQ(57, right);
-  EXPECT_EQ(57, bottom);
-  EXPECT_EQ(57, left);
+  EXPECT_EQ(60, top);
+  EXPECT_EQ(60, right);
+  EXPECT_EQ(60, bottom);
+  EXPECT_EQ(60, left);
 }
 
 TEST(FilterOperationsTest, MapRectBlur) {
@@ -100,10 +100,10 @@ TEST(FilterOperationsTest, GetOutsetsDropShadow) {
   int top, right, bottom, left;
   top = right = bottom = left = 0;
   ops.GetOutsets(&top, &right, &bottom, &left);
-  EXPECT_EQ(49, top);
-  EXPECT_EQ(60, right);
-  EXPECT_EQ(65, bottom);
-  EXPECT_EQ(54, left);
+  EXPECT_EQ(52, top);
+  EXPECT_EQ(63, right);
+  EXPECT_EQ(68, bottom);
+  EXPECT_EQ(57, left);
 }
 
 TEST(FilterOperationsTest, MapRectDropShadow) {