Add an iOS implementation for base::PathService::Get() with path key DIR_APP_DATA.

base/base_paths_mac.mm

Index: base/base_paths_mac.mm
diff --git a/base/base_paths_mac.mm b/base/base_paths_mac.mm
index 56f3ecb9a91e9be5c8888e2f9e53fc04a4cbf64a..ee6c03f6d10ad74bd61eab338e3b3890b319d176 100644
--- a/base/base_paths_mac.mm
+++ b/base/base_paths_mac.mm
@@ -59,8 +59,16 @@ bool PathProviderMac(int key, FilePath* result) {
           reinterpret_cast<const void*>(&base::PathProviderMac));
     case base::DIR_CACHE:
       return base::mac::GetUserDirectory(NSCachesDirectory, result);
-    case base::DIR_APP_DATA:
-      return base::mac::GetUserDirectory(NSApplicationSupportDirectory, result);
+    case base::DIR_APP_DATA: {
+      bool success = base::mac::GetUserDirectory(NSApplicationSupportDirectory,
+                                                 result);
+#if defined(OS_IOS)

[Mark Mentovai, 2012/07/31 23:04:13]

I would say that you don’t have to #ifdef this. It “probably” exists, but
there’s no guarantee in that if someone removes it, I don’t think the OS
automatically recreates it.

But DIR_CACHE doesn’t get the same treatment, and I’d think it’s subject to the
same rules, so I’m inclined to just leave this alone.

[rohitrao (ping after 24h), 2012/07/31 23:08:18]

Ok, will leave this as-is.  It's a two-line CL if we decide otherwise later, but
I don't expect the current code to ever cause any problems in practice.

+      // On IOS, this directory does not exist unless it is created explicitly.
+      if (success && !file_util::PathExists(*result))
+        success = file_util::CreateDirectory(*result);
+#endif  // defined(OS_IOS)
+      return success;
+    }
     case base::DIR_SOURCE_ROOT: {
       // Go through PathService to catch overrides.
       if (!PathService::Get(base::FILE_EXE, result))