`getContextContainer` should be marked as const

Summary: `getContextContainer` should be marked as const so that const instances can call it.

Reviewed By: shergin

Differential Revision: D14969981

fbshipit-source-id: 8812f24ecf0642a38496580689943fbd43cddad1

ReactCommon/fabric/core/componentdescriptor/ComponentDescriptor.cpp

@@ -15,7 +15,8 @@ ComponentDescriptor::ComponentDescriptor(
     ContextContainer::Shared const &contextContainer)
     : eventDispatcher_(eventDispatcher), contextContainer_(contextContainer) {}
 
-ContextContainer::Shared const &ComponentDescriptor::getContextContainer() {
+ContextContainer::Shared const &ComponentDescriptor::getContextContainer()
+    const {
   return contextContainer_;
 }
 

ReactCommon/fabric/core/componentdescriptor/ComponentDescriptor.h

@@ -41,7 +41,7 @@ class ComponentDescriptor {
   /*
    * Returns stored instance of `ContextContainer`.
    */
-  ContextContainer::Shared const &getContextContainer();
+  ContextContainer::Shared const &getContextContainer() const;
 
   /*
    * Returns `componentHandle` associated with particular kind of components.