[intl] Implement Intl.PluralRules

src/i18n.h

Index: src/i18n.h
diff --git a/src/i18n.h b/src/i18n.h
index f89d005b00c844309d925768f231c0bde94ca514..e3258dbe661d71d2ca7217537a450a234f4a6f59 100644
--- a/src/i18n.h
+++ b/src/i18n.h
@@ -14,6 +14,7 @@ class BreakIterator;
 class Collator;
 class DecimalFormat;
 class SimpleDateFormat;
+class PluralRules;
 }
 
 namespace v8 {
@@ -101,6 +102,43 @@ class Collator {
   Collator();
 };
 
+class PluralRules {
+ public:
+  // Create a PluralRules and DecimalFormat for the specificied locale and
+  // options. Returns false on an ICU failure.
+  static bool InitializePluralRules(Isolate* isolate, Handle<String> locale,
+                                    Handle<JSObject> options,
+                                    Handle<JSObject> resolved,
+                                    icu::PluralRules** plural_rules,
+                                    icu::DecimalFormat** decimal_format);
+
+  // Unpacks PluralRules object from corresponding JavaScript object.
+  static icu::PluralRules* UnpackPluralRules(Isolate* isolate,
+                                             Handle<JSObject> obj);
+
+  // Unpacks NumberFormat object from corresponding JavaScript PluralRUles
+  // object.
+  static icu::DecimalFormat* UnpackNumberFormat(Isolate* isolate,
+                                                Handle<JSObject> obj);
+
+  // Release memory we allocated for the Collator once the JS object that holds

[jungshik at Google, 2017/05/08 19:16:54]

Collator?  You mean PluralRules, don't you?

+  // the pointer gets garbage collected.
+  static void DeletePluralRules(const v8::WeakCallbackInfo<void>& data);
+
+  // Layout description.
+  static const int kPluralRules = JSObject::kHeaderSize;
+  // Values are formatted with this NumberFormat and then parsed as a Number
+  // to round them based on the options passed into the PluralRules objct.
+  // TODO(littledan): If a future version of ICU supports the rounding
+  // built-in to PluralRules, switch to that, see this bug:
+  // http://bugs.icu-project.org/trac/ticket/12763

[jungshik at Google, 2017/05/08 19:16:54]

That bug was fixed and is a part of ICU 59.  I'll update ICU to 59.1 before
long, but you don't have to wait for that. We can land first and fix it later
(one ICU is updated to 59.1 for chromium/v8). 

Or you can wait. It's up to you.

[jungshik at Google, 2017/05/19 05:28:34]

FYI, ICU in Chromium tree was updated to 59.1. 

+  static const int kNumberFormat = kPluralRules + kPointerSize;
+  static const int kSize = kNumberFormat + kPointerSize;
+
+ private:
+  PluralRules();
+};
+
 class V8BreakIterator {
  public:
   // Create a BreakIterator for the specificied locale and options. Returns the