Add documentation for platform/bindings

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h

Index: third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
diff --git a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
index f5c9f0b1a3cd0db6c850a30789689b5a13c51b0d..a320871ad5fc8b105ac78ca9c743b29e5f60eb2b 100644
--- a/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
+++ b/third_party/WebKit/Source/platform/bindings/V8PerIsolateData.h
@@ -52,6 +52,8 @@ struct WrapperTypeInfo;
 
 typedef WTF::Vector<DOMDataStore*> DOMDataStoreList;
 
+// Used to hold data that is associated with a single v8::Isolate object, and
+// has a 1:1 relationship with v8::Isolate.
 class PLATFORM_EXPORT V8PerIsolateData {
   USING_FAST_MALLOC(V8PerIsolateData);
   WTF_MAKE_NONCOPYABLE(V8PerIsolateData);