TaskManager: Remove some unused/unnecessary methods.

chrome/browser/task_manager/guest_resource_provider.cc

Index: chrome/browser/task_manager/guest_resource_provider.cc
diff --git a/chrome/browser/task_manager/guest_resource_provider.cc b/chrome/browser/task_manager/guest_resource_provider.cc
index 9d910ab157dd4996f8c9d5e2562776b0664d1dbf..ef06d3766fa848e4b28507767b8b42178d28669d 100644
--- a/chrome/browser/task_manager/guest_resource_provider.cc
+++ b/chrome/browser/task_manager/guest_resource_provider.cc
@@ -43,7 +43,6 @@ class GuestResource : public RendererResource {
   virtual base::string16 GetProfileName() const OVERRIDE;
   virtual gfx::ImageSkia GetIcon() const OVERRIDE;
   virtual content::WebContents* GetWebContents() const OVERRIDE;
-  virtual const extensions::Extension* GetExtension() const OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GuestResource);
@@ -95,10 +94,6 @@ WebContents* GuestResource::GetWebContents() const {
   return WebContents::FromRenderViewHost(render_view_host());
 }
 
-const Extension* GuestResource::GetExtension() const {
-  return NULL;
-}
-
 GuestResourceProvider::GuestResourceProvider(TaskManager* task_manager)
     :  updating_(false),
        task_manager_(task_manager) {