Adding MimeHandlerView.

content/public/renderer/browser_plugin_delegate.h

+#ifndef CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_DELEGATE_H_
+#define CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_DELEGATE_H_
+
+#include <string>
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+// Maybe BrowserPluginLoadObserver?
+class CONTENT_EXPORT BrowserPluginDelegate {
+ public:
+  BrowserPluginDelegate(int routing_id,
+                        int browser_plugin_element_id,
+                        const std::string& mime_type) {}
+  virtual ~BrowserPluginDelegate() {}
+
+  virtual void DidFinishLoading(const std::string& html_string) = 0;
+
+ private:
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_DELEGATE_H_