Implement ManifestManager to handle manifest in content/

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index b840bee4ee6325977a6fe8f12e137082de480c77..b62e9546d38673f5c142b9366848bd223e80a25d 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -57,6 +57,7 @@ class SiteInstance;
 class WebContentsDelegate;
 struct CustomContextMenuContext;
 struct DropData;
+struct Manifest;
 struct RendererPreferences;
 
 // WebContents is the core class in content/. A WebContents renders web content
@@ -579,6 +580,11 @@ class WebContents : public PageNavigator,
   // Returns true if audio has recently been audible from the WebContents.
   virtual bool WasRecentlyAudible() = 0;
 
+  typedef base::Callback<void(const Manifest&)> GetManifestCallback;
+
+  // Requests the Manifest of the main frame's document.
+  virtual void GetManifest(const GetManifestCallback&) = 0;
+
 #if defined(OS_ANDROID)
   CONTENT_EXPORT static WebContents* FromJavaWebContents(
       jobject jweb_contents_android);