Allow extensions of the ManifestParser outside of the content/ layer.

content/public/renderer/content_renderer_client.h

Index: content/public/renderer/content_renderer_client.h
diff --git a/content/public/renderer/content_renderer_client.h b/content/public/renderer/content_renderer_client.h
index a7c727102a4f10c75fdb8c0b2710b7c0f38d51df..cebd366569c4db3b845a3636e4b58d9cfaaeb6e0 100644
--- a/content/public/renderer/content_renderer_client.h
+++ b/content/public/renderer/content_renderer_client.h
@@ -60,6 +60,7 @@ struct KeySystemInfo;
 namespace content {
 class BrowserPluginDelegate;
 class DocumentState;
+class ManifestParser;
 class RenderFrame;
 class RenderView;
 class SynchronousCompositor;
@@ -292,6 +293,11 @@ class CONTENT_EXPORT ContentRendererClient {
   // Returns a user agent override specific for |url|, or empty string if
   // default user agent should be used.
   virtual std::string GetUserAgentOverrideForURL(const GURL& url);
+
+  // Returns whether the default ManifestParser should be overridden.
+  // If returns |true|, |*parser| should be a valid pointer owned by the caller.
+  // Otherwise, |parser| must be null.
+  virtual bool OverrideManifestParser(content::ManifestParser** parser);
 };
 
 }  // namespace content