gn format: penalty-based scheme for line breaking

tools/gn/format_test_data/012.golden

Index: tools/gn/format_test_data/012.golden
diff --git a/tools/gn/format_test_data/012.golden b/tools/gn/format_test_data/012.golden
index 7e3fc989e0214f906f84b6ac2cd0c67ab1f8b320..a0049b2d55dfe36a625214a99ea2a89079395917 100644
--- a/tools/gn/format_test_data/012.golden
+++ b/tools/gn/format_test_data/012.golden
@@ -5,12 +5,18 @@
 
 if (is_win) {
   # This is some special stuff for Windows
-  sources = [ "win.cc" ]
+  sources = [
+    "win.cc",
+  ]
 } else if (is_linux) {
   # This is a block comment inside the linux block, but not attached.
 
-  sources = [ "linux.cc" ]
+  sources = [
+    "linux.cc",
+  ]
 } else {
   # A comment with trailing spaces
-  sources = [ "wha.cc" ]
+  sources = [
+    "wha.cc",
+  ]
 }