Add a mimeHandler extension API.

chrome/browser/extensions/api/streams_private/streams_private_api.h

Index: chrome/browser/extensions/api/streams_private/streams_private_api.h
diff --git a/chrome/browser/extensions/api/streams_private/streams_private_api.h b/chrome/browser/extensions/api/streams_private/streams_private_api.h
index 47a92a79781118c644c42f709bf15bd0060bf8a1..42081a64fa326f985806cac7800dc03bf457fd40 100644
--- a/chrome/browser/extensions/api/streams_private/streams_private_api.h
+++ b/chrome/browser/extensions/api/streams_private/streams_private_api.h
@@ -58,9 +58,6 @@ class StreamsPrivateAPI : public BrowserContextKeyedAPI,
   typedef std::map<std::string,
                    std::map<GURL,
                             linked_ptr<content::StreamHandle> > > StreamMap;
-  using MimeHandlerStreamMap =
-      std::map<std::string,
-               std::map<GURL, std::pair<content::WebContents*, std::string>>>;
 
   // ExtensionRegistryObserver implementation.
   void OnExtensionUnloaded(content::BrowserContext* browser_context,
@@ -77,9 +74,6 @@ class StreamsPrivateAPI : public BrowserContextKeyedAPI,
   content::BrowserContext* const browser_context_;
   StreamMap streams_;
 
-  // The streams whose lifetimes are managed by MimeHandlerViewGuest.
-  MimeHandlerStreamMap mime_handler_streams_;
-
   // Listen to extension unloaded notifications.
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;