Fix aligning of comments.

Previously we started sequences to align for single line comments when
the previous line had a trailing comment, but the sequence was broken
for other reasons.

Now we re-format:
// a
 // b
f(); // c
to:
// a
// b
f(); // c

llvm-svn: 182608
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 5346bdc..ce551e9 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -657,6 +657,26 @@
             format("lineWith();   // comment\n"
                    "// at start\n"
                    "otherLine();   // comment"));
+  EXPECT_EQ("lineWith();\n"
+            "// at start\n"
+            "otherLine(); // comment",
+            format("lineWith();\n"
+                   " // at start\n"
+                   "otherLine();   // comment"));
+  EXPECT_EQ("// first\n"
+            "// at start\n"
+            "otherLine(); // comment",
+            format("// first\n"
+                   " // at start\n"
+                   "otherLine();   // comment"));
+  EXPECT_EQ("f();\n"
+            "// first\n"
+            "// at start\n"
+            "otherLine(); // comment",
+            format("f();\n"
+                   "// first\n"
+                   " // at start\n"
+                   "otherLine();   // comment"));
 }
 
 TEST_F(FormatTest, CanFormatCommentsLocally) {