Index: lib/Format/BreakableToken.h
===================================================================
--- lib/Format/BreakableToken.h
+++ lib/Format/BreakableToken.h
@@ -121,7 +121,8 @@
   /// For breakable tokens that never use extra space at the end of a line, this
   /// is equivalent to getRangeLength with a Length of StringRef::npos.
   virtual unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
-                                      unsigned StartColumn) const {
+                                      unsigned StartColumn,
+                                      bool CanBreakAfter) const {
     return getRangeLength(LineIndex, Offset, StringRef::npos, StartColumn);
   }
 
@@ -253,7 +254,8 @@
                           StringRef::size_type Length,
                           unsigned StartColumn) const override;
   unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
-                              unsigned StartColumn) const override;
+                              unsigned StartColumn,
+                              bool CanBreakAfter) const override;
   unsigned getContentStartColumn(unsigned LineIndex, bool Break) const override;
 
 protected:
@@ -352,7 +354,8 @@
                           StringRef::size_type Length,
                           unsigned StartColumn) const override;
   unsigned getRemainingLength(unsigned LineIndex, unsigned Offset,
-                              unsigned StartColumn) const override;
+                              unsigned StartColumn,
+                              bool CanBreakAfter) const override;
   unsigned getContentStartColumn(unsigned LineIndex, bool Break) const override;
   void insertBreak(unsigned LineIndex, unsigned TailOffset, Split Split,
                    WhitespaceManager &Whitespaces) const override;
Index: lib/Format/BreakableToken.cpp
===================================================================
--- lib/Format/BreakableToken.cpp
+++ lib/Format/BreakableToken.cpp
@@ -199,10 +199,11 @@
                    "indicates that the code tries to reflow it.");
 }
 
-unsigned
-BreakableStringLiteral::getRemainingLength(unsigned LineIndex, unsigned Offset,
-                                           unsigned StartColumn) const {
-  return UnbreakableTailLength + Postfix.size() +
+unsigned BreakableStringLiteral::getRemainingLength(unsigned LineIndex,
+                                                    unsigned Offset,
+                                                    unsigned StartColumn,
+                                                    bool CanBreakAfter) const {
+  return (CanBreakAfter ? 0 : UnbreakableTailLength) + Postfix.size() +
          encoding::columnWidthWithTabs(Line.substr(Offset, StringRef::npos),
                                        StartColumn, Style.TabWidth, Encoding);
 }
@@ -497,7 +498,8 @@
 
 unsigned BreakableBlockComment::getRemainingLength(unsigned LineIndex,
                                                    unsigned Offset,
-                                                   unsigned StartColumn) const {
+                                                   unsigned StartColumn,
+                                                   bool CanBreakAfter) const {
   return UnbreakableTailLength +
          getRangeLength(LineIndex, Offset, StringRef::npos, StartColumn);
 }
Index: lib/Format/ContinuationIndenter.cpp
===================================================================
--- lib/Format/ContinuationIndenter.cpp
+++ lib/Format/ContinuationIndenter.cpp
@@ -1619,7 +1619,8 @@
     // We don't insert backslashes when breaking line comments.
     ColumnLimit = Style.ColumnLimit;
   }
-  if (Current.UnbreakableTailLength >= ColumnLimit)
+  bool CanBreakAfter = State.NextToken && canBreak(State);
+  if (!CanBreakAfter && Current.UnbreakableTailLength >= ColumnLimit)
     return {0, false};
   // ColumnWidth was already accounted into State.Column before calling
   // breakProtrudingToken.
@@ -1646,8 +1647,8 @@
   unsigned ContentStartColumn =
       Token->getContentStartColumn(0, /*Break=*/false);
   // The number of columns left in the current logical line after TailOffset.
-  unsigned RemainingTokenColumns =
-      Token->getRemainingLength(0, TailOffset, ContentStartColumn);
+  unsigned RemainingTokenColumns = Token->getRemainingLength(
+      0, TailOffset, ContentStartColumn, CanBreakAfter);
   // Adapt the start of the token, for example indent.
   if (!DryRun)
     Token->adaptStartOfLine(0, Whitespaces);
@@ -1721,8 +1722,8 @@
         // into the current line.
         unsigned ToNextSplitColumns = 0;
         if (NextSplit.first == StringRef::npos) {
-          ToNextSplitColumns = Token->getRemainingLength(LineIndex, TailOffset,
-                                                         ContentStartColumn);
+          ToNextSplitColumns = Token->getRemainingLength(
+              LineIndex, TailOffset, ContentStartColumn, CanBreakAfter);
         } else {
           ToNextSplitColumns = Token->getRangeLength(
               LineIndex, TailOffset,
@@ -1767,7 +1768,7 @@
           Penalty += ExcessCharactersPenalty;
           TailOffset += Split.first + Split.second;
           RemainingTokenColumns = Token->getRemainingLength(
-              LineIndex, TailOffset, ContentStartColumn);
+              LineIndex, TailOffset, ContentStartColumn, CanBreakAfter);
           continue;
         }
       }
@@ -1776,7 +1777,7 @@
           Token->getContentStartColumn(LineIndex, /*Break=*/true);
       unsigned NewRemainingTokenColumns = Token->getRemainingLength(
           LineIndex, TailOffset + Split.first + Split.second,
-          ContentStartColumn);
+          ContentStartColumn, CanBreakAfter);
 
       // When breaking before a tab character, it may be moved by a few columns,
       // but will still be expanded to the next tab stop, so we don't save any
@@ -1835,7 +1836,7 @@
           // If the rest of the next line fits into the current line below the
           // column limit, we can safely reflow.
           RemainingTokenColumns = Token->getRemainingLength(
-              NextLineIndex, TailOffset, ContentStartColumn);
+              NextLineIndex, TailOffset, ContentStartColumn, CanBreakAfter);
           Reflow = true;
           if (ContentStartColumn + RemainingTokenColumns > ColumnLimit) {
             DEBUG(llvm::dbgs() << "    Over limit after reflow, need: "
@@ -1884,7 +1885,7 @@
         ContentStartColumn =
             Token->getContentStartColumn(NextLineIndex, /*Break=*/false);
         RemainingTokenColumns = Token->getRemainingLength(
-            NextLineIndex, TailOffset, ContentStartColumn);
+            NextLineIndex, TailOffset, ContentStartColumn, CanBreakAfter);
         // Adapt the start of the token, for example indent.
         if (!DryRun)
           Token->adaptStartOfLine(NextLineIndex, Whitespaces);
@@ -1924,7 +1925,7 @@
     RemainingTokenColumns = Token->getRemainingLength(
         Token->getLineCount() - 1,
         TailOffset + SplitAfterLastLine.first + SplitAfterLastLine.second,
-        ContentStartColumn);
+        ContentStartColumn, CanBreakAfter);
   }
 
   State.Column = ContentStartColumn + RemainingTokenColumns -
Index: unittests/Format/FormatTestTextProto.cpp
===================================================================
--- unittests/Format/FormatTestTextProto.cpp
+++ unittests/Format/FormatTestTextProto.cpp
@@ -290,5 +290,17 @@
                "  product_data <product {1}>\n"
                ">");
 }
+
+TEST_F(FormatTestTextProto, DiscardsUnbreakableTailIfCanBreakAfter) {
+  // The two closing braces count towards the string UnbreakableTailLength, but
+  // since we have broken after the corresponding opening braces, we don't
+  // consider that length for string breaking.
+  verifyFormat(
+      "foo: {\n"
+      "  bar: {\n"
+      "    text: \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\"\n"
+      "  }\n"
+      "}");
+}
 } // end namespace tooling
 } // end namespace clang