[clang-format] Add SpaceBeforeCpp11BracedList option.

WebKit C++ style for object initialization is as follows:

  Foo foo { bar };

Yet using clang-format -style=webkit changes this to:

  Foo foo{ bar };

As there is no existing combination of rules that will ensure a space
before a braced list in this fashion, this patch adds a new
SpaceBeforeCpp11BracedList rule.

Patch by Ross Kirsling!

Differential Revision: https://reviews.llvm.org/D46024

llvm-svn: 334692
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index ea95769..3280f25 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -2548,6 +2548,9 @@
   if (Style.isCpp()) {
     if (Left.is(tok::kw_operator))
       return Right.is(tok::coloncolon);
+    if (Right.is(tok::l_brace) && Right.BlockKind == BK_BracedInit &&
+        !Left.opensScope() && Style.SpaceBeforeCpp11BracedList)
+      return true;
   } else if (Style.Language == FormatStyle::LK_Proto ||
              Style.Language == FormatStyle::LK_TextProto) {
     if (Right.is(tok::period) &&