Fixes indent in linkage specification blocks.

We now indent:
extern "C" {
int a;
}

without additional indent inside the extern "C" block.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173045 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/UnwrappedLineParser.cpp

@@ -311,6 +311,18 @@ void UnwrappedLineParser::parseStructuralElement() {
   case tok::kw_return:
     parseReturn();
     return;
+  case tok::kw_extern:
+    nextToken();
+    if (FormatTok.Tok.is(tok::string_literal)) {
+      nextToken();
+      if (FormatTok.Tok.is(tok::l_brace)) {
+        parseBlock(0);
+        addUnwrappedLine();
+        return;
+      }
+    }
+    // In all other cases, parse the declaration.
+    break;
   default:
     break;
   }

unittests/Format/FormatTest.cpp

@@ -526,6 +526,10 @@ TEST_F(FormatTest, FormatsNamespaces) {
                "void f() { f(); }");
 }
 
+TEST_F(FormatTest, FormatsExternC) {
+  verifyFormat("extern \"C\" {\nint a;");
+}
+
 TEST_F(FormatTest, FormatTryCatch) {
   // FIXME: Handle try-catch explicitly in the UnwrappedLineParser, then we'll
   // also not create single-line-blocks.