Update a couple of stale process-per-site comments about WebUI.

We no longer use process-per-site for WebUI (see crbug.com/982266), so
fix a couple of comments that implied that we do.

Bug: 1015882, 982266
Change-Id: I639c5b0b159c5e88f15263fdab01dc2dec95b33b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2151681Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760289}

content/browser/renderer_host/render_process_host_impl.cc

@@ -4194,9 +4194,8 @@ bool RenderProcessHost::ShouldUseProcessPerSite(BrowserContext* browser_context,
                                                 const GURL& url) {
   // Returns true if we should use the process-per-site model.  This will be
   // the case if the --process-per-site switch is specified, or in
-  // process-per-site-instance for particular sites (e.g., WebUI).
-  // Note that --single-process is handled in
-  // ShouldTryToUseExistingProcessHost.
+  // process-per-site-instance for particular sites (e.g., NTP). Note that
+  // --single-process is handled in ShouldTryToUseExistingProcessHost.
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kProcessPerSite))

content/public/browser/site_instance.h

@@ -96,7 +96,7 @@ class CONTENT_EXPORT SiteInstance : public base::RefCounted<SiteInstance> {
   // RenderProcessHost (and a new ID).  Note that renderer process crashes leave
   // the current RenderProcessHost (and ID) in place.
   //
-  // For sites that require process-per-site mode (e.g., WebUI), this will
+  // For sites that require process-per-site mode (e.g., NTP), this will
   // ensure only one RenderProcessHost for the site exists within the
   // BrowserContext.
   virtual content::RenderProcessHost* GetProcess() = 0;
@@ -167,8 +167,10 @@ class CONTENT_EXPORT SiteInstance : public base::RefCounted<SiteInstance> {
 
   // Factory method to get the appropriate SiteInstance for the given URL, in
   // a new BrowsingInstance.  Use this instead of Create when you know the URL,
-  // since it allows special site grouping rules to be applied (for example,
-  // to group chrome-ui pages into the same instance).
+  // since it allows special site grouping rules to be applied (for example, to
+  // obey process-per-site for sites that require it, such as NTP, or to use a
+  // default SiteInstance for sites that don't require a dedicated process on
+  // Android).
   static scoped_refptr<SiteInstance> CreateForURL(
       content::BrowserContext* browser_context,
       const GURL& url);