No need to call FilterURL on trustworthy data in RFHI::ShowContextMenu.

Before this CL, RenderFrameHostImpl::ShowContextMenu would call
`process->FilterURL(...page_url)`.  This call was

1) Incorrect: using `this` frame's (potentially subframe's) process
   to filter the URL of the main frame (`page_url` comes from
   `GetMainFrame()->GetLastCommittedURL()` called a few lines above).

2) Unnecessary: `page_url` is trustworthy (i.e. populated on
   browser-side data, rather than based on
   UntrustworthyContextMenuParams).

After this CL, RenderFrameHostImpl::ShowContextMenu no longer calls
FilterURL on A) `page_url` and B) `frame_url` (both of these are
based on trustworthy data).

Bug: 1257907
Change-Id: I9ed7e0311af5287da668e07d582caa6445fc3f92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3223130
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#931788}

content/browser/renderer_host/render_frame_host_impl.cc

@@ -6230,16 +6230,15 @@ void RenderFrameHostImpl::ShowContextMenu(
   // directly, don't show them in the context menu.
   ContextMenuParams validated_params(params);
   validated_params.page_url = GetMainFrame()->GetLastCommittedURL();
-  if (GetParent())  // Only populate |frame_url| for subframes.
-    validated_params.frame_url = GetLastCommittedURL();
+  // Only populate |frame_url| if `this` is actually a subframe.
+  validated_params.frame_url = GetParent() ? GetLastCommittedURL() : GURL();
 
   // We don't validate |unfiltered_link_url| so that this field can be used
-  // when users want to copy the original link URL.
+  // when users want to copy the original link URL.  We also don't filter the
+  // URLs based on trustworthy data (e.g. `page_url` and `frame_url`).
   RenderProcessHost* process = GetProcess();
   process->FilterURL(true, &validated_params.link_url);
   process->FilterURL(true, &validated_params.src_url);
-  process->FilterURL(false, &validated_params.page_url);
-  process->FilterURL(true, &validated_params.frame_url);
 
   // It is necessary to transform the coordinates to account for nested
   // RenderWidgetHosts, such as with out-of-process iframes.