[Extensions] Clean up the handling of ExtensionHostMsg_Request

extensions/browser/extension_function_dispatcher.cc

Index: extensions/browser/extension_function_dispatcher.cc
diff --git a/extensions/browser/extension_function_dispatcher.cc b/extensions/browser/extension_function_dispatcher.cc
index e682701bc3f257d7ac950e4d1b376dfe3b16def7..7458159653186005ad5432b17c8139122b3de6f2 100644
--- a/extensions/browser/extension_function_dispatcher.cc
+++ b/extensions/browser/extension_function_dispatcher.cc
@@ -205,12 +205,12 @@ class ExtensionFunctionDispatcher::UIThreadResponseCallbackWrapper
 
 WindowController*
 ExtensionFunctionDispatcher::Delegate::GetExtensionWindowController() const {
-  return NULL;
+  return nullptr;
 }
 
 content::WebContents*
 ExtensionFunctionDispatcher::Delegate::GetAssociatedWebContents() const {
-  return NULL;
+  return nullptr;
 }
 
 content::WebContents*
@@ -301,10 +301,8 @@ void ExtensionFunctionDispatcher::DispatchOnIOThread(
 }
 
 ExtensionFunctionDispatcher::ExtensionFunctionDispatcher(
-    content::BrowserContext* browser_context,
-    Delegate* delegate)
-    : browser_context_(browser_context),
-      delegate_(delegate) {
+    content::BrowserContext* browser_context)
+    : browser_context_(browser_context) {
 }
 
 ExtensionFunctionDispatcher::~ExtensionFunctionDispatcher() {
@@ -440,6 +438,22 @@ void ExtensionFunctionDispatcher::OnExtensionFunctionCompleted(
   }
 }
 
+WindowController*
+ExtensionFunctionDispatcher::GetExtensionWindowController() const {
+  return delegate_ ? delegate_->GetExtensionWindowController() : nullptr;
+}
+
+content::WebContents*
+ExtensionFunctionDispatcher::GetAssociatedWebContents() const {
+  return delegate_ ? delegate_->GetAssociatedWebContents() : nullptr;
+}
+
+content::WebContents*
+ExtensionFunctionDispatcher::GetVisibleWebContents() const {
+  return delegate_ ? delegate_->GetVisibleWebContents() :
+      GetAssociatedWebContents();
+}
+
 // static
 bool ExtensionFunctionDispatcher::CheckPermissions(
     ExtensionFunction* function,