Clean up rewrite_to_chrome_style naming logic.

tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp

Index: tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
diff --git a/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp b/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
index 9bcf3c120514c75c6b9e53b61888ff7065ee9855..333687fb6cfda3cdeffad20c2e4ce5ee729d13ed 100644
--- a/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
+++ b/tools/clang/rewrite_to_chrome_style/RewriteToChromeStyle.cpp
@@ -33,6 +33,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/TargetSelect.h"
+#include "tools/clang/rewrite_to_chrome_style/Renamer.h"
 
 using namespace clang::ast_matchers;
 using clang::tooling::CommonOptionsParser;
@@ -50,45 +51,10 @@ constexpr char kBlinkFieldPrefix[] = "m_";
 constexpr char kBlinkStaticMemberPrefix[] = "s_";
 
 bool GetNameForDecl(const clang::FunctionDecl& decl, std::string& name) {
-  name = decl.getNameAsString();
-  name[0] = clang::toUppercase(name[0]);
+  name = IdentifierToCamelCase(decl.getName());
   return true;
 }
 
-// Helper to convert from a camelCaseName to camel_case_name. It uses some
-// heuristics to try to handle acronyms in camel case names correctly.
-std::string CamelCaseToUnderscoreCase(StringRef input) {
-  std::string output;
-  bool needs_underscore = false;
-  bool was_lowercase = false;
-  bool was_uppercase = false;
-  // Iterate in reverse to minimize the amount of backtracking.
-  for (const unsigned char* i = input.bytes_end() - 1; i >= input.bytes_begin();
-       --i) {
-    char c = *i;
-    bool is_lowercase = clang::isLowercase(c);
-    bool is_uppercase = clang::isUppercase(c);
-    c = clang::toLowercase(c);
-    // Transitioning from upper to lower case requires an underscore. This is
-    // needed to handle names with acronyms, e.g. handledHTTPRequest needs a '_'
-    // in 'dH'. This is a complement to the non-acronym case further down.
-    if (needs_underscore || (was_uppercase && is_lowercase)) {
-      output += '_';
-      needs_underscore = false;
-    }
-    output += c;
-    // Handles the non-acronym case: transitioning from lower to upper case
-    // requires an underscore when emitting the next character, e.g. didLoad
-    // needs a '_' in 'dL'.
-    if (i != input.bytes_end() - 1 && was_lowercase && is_uppercase)
-      needs_underscore = true;
-    was_lowercase = is_lowercase;
-    was_uppercase = is_uppercase;
-  }
-  std::reverse(output.begin(), output.end());
-  return output;
-}
-
 bool GetNameForDecl(const clang::FieldDecl& decl, std::string& name) {
   StringRef original_name = decl.getName();
   // Blink style field names are prefixed with `m_`. If this prefix isn't
@@ -96,7 +62,7 @@ bool GetNameForDecl(const clang::FieldDecl& decl, std::string& name) {
   if (original_name.size() < strlen(kBlinkFieldPrefix) ||
       !original_name.startswith(kBlinkFieldPrefix))
     return false;
-  name = CamelCaseToUnderscoreCase(
+  name = IdentifierToUnderscoreCase(
       original_name.substr(strlen(kBlinkFieldPrefix)));
   // The few examples I could find used struct-style naming with no `_` suffix
   // for unions.
@@ -162,10 +128,9 @@ bool GetNameForDecl(const clang::VarDecl& decl, std::string& name) {
         clang::isUppercase(original_name[1]))
       return false;
     name = 'k';
-    name.append(original_name.data(), original_name.size());
-    name[1] = clang::toUppercase(name[1]);
+    name += IdentifierToCamelCase(original_name);
   } else {
-    name = CamelCaseToUnderscoreCase(original_name);
+    name = IdentifierToUnderscoreCase(original_name);
   }
 
   if (decl.isStaticDataMember()) {