chrome_paths: refactor and sanitize cache directory handling

chrome/common/chrome_paths_mac.mm

Index: chrome/common/chrome_paths_mac.mm
diff --git a/chrome/common/chrome_paths_mac.mm b/chrome/common/chrome_paths_mac.mm
index b87b39788ecd09ae100c4a9eef4fedc03dfdf6bb..11494f822defab1e0dfa356f44e167449fd75e52 100644
--- a/chrome/common/chrome_paths_mac.mm
+++ b/chrome/common/chrome_paths_mac.mm
@@ -48,6 +48,30 @@ bool GetUserDocumentsDirectory(FilePath* result) {
   return mac_util::GetUserDirectory(NSDocumentDirectory, result);
 }
 
+bool GetUserCacheDirectory(const FilePath& profile_dir, FilePath* result) {
+  // If the profile directory is under ~/Library/Application Support,
+  // use a suitable cache directory under ~/Library/Caches.  For
+  // example, a profile directory of ~/Library/Application
+  // Support/Google/Chrome/MyProfileName would use the cache directory
+  // ~/Library/Caches/Google/Chrome/MyProfileName.
+
+  FilePath cache_dir;
+  if (!mac_util::GetUserDirectory(NSCachesDirectory, &cache_dir))
+    return false;
+
+  FilePath app_data_dir;
+  if (PathService::Get(base::DIR_APP_DATA, &app_data_dir)) {
+    FilePath system_relative_dir = cache_dir;

[Mark Mentovai, 2010/11/18 16:54:54]

Do you need this copy? Why don’t you just move the GetUserDirectory call right
here and have it fill in system_relative_dir?

[Evan Martin, 2010/11/18 18:13:07]

I found the usage of AppendRelativePath kind of hard to follow, so I thought the
extra naming would help.  I'll try a different approach.

+    if (app_data_dir.AppendRelativePath(profile_dir, &system_relative_dir)) {
+      *result = system_relative_dir;
+      return true;
+    }
+  }
+
+  *result = profile_dir;
+  return true;
+}
+
 bool GetUserDownloadsDirectory(FilePath* result) {
   return mac_util::GetUserDirectory(NSDownloadsDirectory, result);
 }