clang tools: Add --bootstrap to the documentation for update.py

tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp

 // Copyright 2015 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.
 //
 // Changes Blink-style names to Chrome-style names. Currently transforms:
 //   fields:
 //     int m_operationCount => int operation_count_
 //   variables (including parameters):
 //     int mySuperVariable => int my_super_variable
 //   constants:
@@ skipping 93 matching lines @@
   StringRef original_name = decl.getName();
   // Blink style field names are prefixed with `m_`. If this prefix isn't
   // present, assume it's already been converted to Google style.
   if (original_name.size() < strlen(kBlinkFieldPrefix) ||
       !original_name.startswith(kBlinkFieldPrefix))
     return false;
   name = CamelCaseToUnderscoreCase(
       original_name.substr(strlen(kBlinkFieldPrefix)));
   // The few examples I could find used struct-style naming with no `_` suffix
   // for unions.
-  if (decl.getParent()->isClass())
+  bool c = decl.getParent()->isClass();
+  // There appears to be a GCC bug that makes this branch incorrectly if we
+  // don't use a temp variable!! Clang works right. crbug.com/580745
+  if (c)

[dcheng, 2016/01/27 23:46:15]

This gives me the heebie jeebies. I feel like we shouldn't check in code like
this, because if we can't trust the compiler, then there's basically nothing we
can do, right? We basically don't have a way to guarantee that this will work
since it's really hard to test.

[danakj, 2016/01/27 23:51:01]

Ya, I'm sure there's other bugs happening elsewhere too, heh. I just don't like
leaving the one I know here malfunctioning, just cuz.. you think it's better to
cover our eyes on this one place and just say don't use gcc?

     name += '_';
   return true;
 }
 
 bool IsProbablyConst(const clang::VarDecl& decl,
                      const clang::ASTContext& context) {
   clang::QualType type = decl.getType();
   if (!type.isConstQualified())
     return false;
 
@@ skipping 430 matching lines @@
   for (const auto& r : replacements) {
     std::string replacement_text = r.getReplacementText().str();
     std::replace(replacement_text.begin(), replacement_text.end(), '\n', '\0');
     llvm::outs() << "r:::" << r.getFilePath() << ":::" << r.getOffset()
                  << ":::" << r.getLength() << ":::" << replacement_text << "\n";
   }
   llvm::outs() << "==== END EDITS ====\n";
 
   return 0;
 }