gn format: properly break and align multiple suffix comments

tools/gn/command_format.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sstream>
 
 #include "base/command_line.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parser.h"
@@ skipping 104 matching lines @@
 void Printer::TrimAndPrintToken(const Token& token) {
   std::string trimmed;
   TrimWhitespaceASCII(token.value().as_string(), base::TRIM_ALL, &trimmed);
   Print(trimmed);
 }
 
 void Printer::Newline() {
   if (!comments_.empty()) {
     Print("  ");
     int i = 0;
+    // Save the margin, and temporarily set it to where the first comment
+    // starts so that multiple suffix comments are vertically aligned. This
+    // will need to be fancier once we enforce 80 col.
+    int old_margin = margin_;
     for (const auto& c : comments_) {
-      if (i > 0) {
+      if (i == 0)
+        margin_ = CurrentColumn();
+      else {
         Trim();
         Print("\n");
         PrintMargin();
       }
       TrimAndPrintToken(c);
+      ++i;
     }
+    margin_ = old_margin;
     comments_.clear();
   }
   Trim();
   Print("\n");
   PrintMargin();
 }
 
 void Printer::Trim() {
   size_t n = output_.size();
   while (n > 0 && output_[n - 1] == ' ')
@@ skipping 277 matching lines @@
   }
   std::string output_string;
   if (FormatFileToString(input_name, dump_tree, &output_string)) {
     printf("%s", output_string.c_str());
   }
 
   return 0;
 }
 
 }  // namespace commands