[clang-format] Ignore UnbreakableTailLength sometimes during breaking

Summary:
This patch fixes an issue where the UnbreakableTailLength would be counted towards
the length of a token during breaking, even though we can break after the token.

For example, this proto text with column limit 20
```
# ColumnLimit: 20  V
foo: {
  bar: {
    bazoo: "aaaaaaa"
  }
}
```
was broken:
```
# ColumnLimit: 20  V
foo: {
  bar: {
    bazoo:
        "aaaaaaa"
  }
}
```
because the 2 closing `}` were counted towards the string literal's `UnbreakableTailLength`.

Reviewers: djasper

Reviewed By: djasper

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D42376

llvm-svn: 323188
diff --git a/clang/lib/Format/BreakableToken.h b/clang/lib/Format/BreakableToken.h
index 8ef26ef..eba48f7 100644
--- a/clang/lib/Format/BreakableToken.h
+++ b/clang/lib/Format/BreakableToken.h
@@ -238,8 +238,8 @@
   /// after formatting.
   BreakableStringLiteral(const FormatToken &Tok, unsigned StartColumn,
                          StringRef Prefix, StringRef Postfix,
-                         bool InPPDirective, encoding::Encoding Encoding,
-                         const FormatStyle &Style);
+                         unsigned UnbreakableTailLength, bool InPPDirective,
+                         encoding::Encoding Encoding, const FormatStyle &Style);
 
   Split getSplit(unsigned LineIndex, unsigned TailOffset, unsigned ColumnLimit,
                  unsigned ReflowColumn,