[api] Add documentation for SetHandler().

BUG=v8:5260

Review-Url: https://codereview.chromium.org/2263363002
Cr-Commit-Position: refs/heads/master@{#38831}

include/v8.h

@@ -4778,6 +4778,18 @@ class V8_EXPORT ObjectTemplate : public Template {
                                NamedPropertyDeleterCallback deleter = 0,
                                NamedPropertyEnumeratorCallback enumerator = 0,
                                Local<Value> data = Local<Value>());
+
+  /**
+   * Sets a named property handler on the object template.
+   *
+   * Whenever a property whose name is a string or a symbol is accessed on
+   * objects created from this object template, the provided callback is
+   * invoked instead of accessing the property directly on the JavaScript
+   * object.
+   *
+   * @param configuration The NamedPropertyHandlerConfiguration that defines the
+   * callbacks to invoke when accessing a property.
+   */
   void SetHandler(const NamedPropertyHandlerConfiguration& configuration);
 
   /**
@@ -4807,6 +4819,17 @@ class V8_EXPORT ObjectTemplate : public Template {
     SetHandler(IndexedPropertyHandlerConfiguration(getter, setter, query,
                                                    deleter, enumerator, data));
   }
+
+  /**
+   * Sets an indexed property handler on the object template.
+   *
+   * Whenever an indexed property is accessed on objects created from
+   * this object template, the provided callback is invoked instead of
+   * accessing the property directly on the JavaScript object.
+   *
+   * @param configuration The IndexedPropertyHandlerConfiguration that defines
+   * the callbacks to invoke when accessing a property.
+   */
   void SetHandler(const IndexedPropertyHandlerConfiguration& configuration);
 
   /**