Ensure streams aren't intercepted unless their associated plugin is enabled

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

Index: chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
diff --git a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
index 8bf559c1a6eece3df09a3c6062f8c809270b2f32..d77f658da9dc8ed4e45d80505fef727ec9b2718f 100644
--- a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
+++ b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
@@ -16,6 +16,7 @@
 #include "chrome/browser/download/download_request_limiter.h"
 #include "chrome/browser/download/download_resource_throttle.h"
 #include "chrome/browser/net/resource_prefetch_predictor_observer.h"
+#include "chrome/browser/plugins/plugin_prefs.h"
 #include "chrome/browser/prefetch/prefetch.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
@@ -37,6 +38,8 @@
 #include "components/variations/net/variations_http_header_provider.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
+#include "content/public/browser/plugin_service.h"
+#include "content/public/browser/plugin_service_filter.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/resource_context.h"
@@ -207,6 +210,37 @@ void SendExecuteMimeTypeHandlerEvent(scoped_ptr<content::StreamInfo> stream,
       extension_id, web_contents, stream.Pass(), view_id, expected_content_size,
       embedded, render_process_id, render_frame_id);
 }
+
+// TODO(raymes): This won't return the right result if plugins haven't been
+// loaded yet. Fixing this properly really requires fixing crbug.com/443466.
+bool IsPluginEnabledForExtension(const Extension* extension,
+                                 const ResourceRequestInfo* info,
+                                 const std::string& mime_type,
+                                 const GURL& url) {
+  content::PluginService* service = content::PluginService::GetInstance();
+  std::vector<content::WebPluginInfo> plugins;
+  service->GetPluginInfoArray(
+      url, mime_type, true, &plugins, nullptr);

[Sam McNally, 2015/02/23 00:38:35]

This looks like it can fit on the previous line.

[raymes, 2015/02/23 02:26:13]

Done.

+  content::PluginServiceFilter* filter = service->GetFilter();
+
+  for (size_t i = 0; i < plugins.size(); ++i) {

[Sam McNally, 2015/02/23 00:38:34]

for-each loop?

[raymes, 2015/02/23 02:26:13]

Done.

+    // Check that the plugin is running the extension.
+    if (plugins[i].path !=
+        base::FilePath::FromUTF8Unsafe(extension->url().spec())) {
+      continue;
+    }
+    // Check that the plugin is actually enabled.
+    if (!filter || filter->IsPluginAvailable(info->GetChildID(),
+                                             info->GetRenderFrameID(),
+                                             info->GetContext(),
+                                             url,
+                                             GURL(),
+                                             &plugins[i])) {
+      return true;
+    }
+  }
+  return false;
+}
 #endif  // !defined(ENABLE_EXTENSIONS)
 
 #if !defined(OS_ANDROID)
@@ -627,6 +661,13 @@ bool ChromeResourceDispatcherHostDelegate::ShouldInterceptResourceAsStream(
       *origin = Extension::GetBaseURLFromExtensionId(extension_id);
       target_info.extension_id = extension_id;
       if (!handler->handler_url().empty()) {
+        // This is reached in the case of MimeHandlerViews. If the
+        // MimeHandlerView plugin is disabled, then we shouldn't intercept the
+        // stream.
+        if (!IsPluginEnabledForExtension(extension, info, mime_type,
+                                         request->url())) {
+          continue;
+        }
         target_info.view_id = base::GenerateGUID();
         *payload = target_info.view_id;
       }