Create MimeHandlerViewFrameContainer only once

Currently embedding a PDF creates a MimeHandlerViewFrameContainer which
then loads an extension that attaches another internal plugin element
to load the PDF plugin. This CL makes sure we do not create a second
MimeHandlerViewFrameContainer for that.

Bug: 659750
Change-Id: Iff71eee6d59b824572628f1ba68651d6be16138c
Reviewed-on: https://chromium-review.googlesource.com/c/1265502
Commit-Queue: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597284}

extensions/browser/guest_view/mime_handler_view/mime_handler_view_browsertest.cc

@@ -32,6 +32,7 @@
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "net/test/embedded_test_server/http_request.h"
 #include "services/network/public/cpp/features.h"
+#include "url/url_constants.h"
 
 using extensions::ExtensionsAPIClient;
 using extensions::MimeHandlerViewGuest;
@@ -157,6 +158,11 @@ INSTANTIATE_TEST_CASE_P(/* no prefix */,
 
 IN_PROC_BROWSER_TEST_P(MimeHandlerViewCrossProcessTest, Embedded) {
   RunTest("test_embedded.html");
+  // Sanity check. Navigate the page and verify the guest goes away.
+  ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL));
+  auto* gv_manager = GetGuestViewManager();
+  gv_manager->WaitForAllGuestsDeleted();
+  EXPECT_EQ(1U, gv_manager->num_guests_created());
 }
 
 // The following tests will eventually converted into a parametric version which

extensions/renderer/guest_view/mime_handler_view/mime_handler_view_frame_container.cc

@@ -35,6 +35,13 @@ bool MimeHandlerViewFrameContainer::Create(
     const std::string& mime_type,
     const content::WebPluginInfo& plugin_info,
     int32_t element_instance_id) {
+  if (plugin_info.type != content::WebPluginInfo::PLUGIN_TYPE_BROWSER_PLUGIN) {
+    // TODO(ekaramad): Rename this plugin type once https://crbug.com/659750 is
+    // fixed. We only create a MHVFC for the plugin types of BrowserPlugin
+    // (which used to create a MimeHandlerViewContainer).
+    return false;
+  }
+
   if (!IsSupportedMimeType(mime_type))
     return false;
   // Life time is managed by the class itself: when the MimeHandlerViewGuest