webapk: Avoid overwriting default CreationParams

content/public/browser/site_instance.h

Index: content/public/browser/site_instance.h
diff --git a/content/public/browser/site_instance.h b/content/public/browser/site_instance.h
index 2d1a9a3dbca452b0964bcfe8c70225192839f595..4b75a1b3eb0f045b9177542c4ad061a998316908 100644
--- a/content/public/browser/site_instance.h
+++ b/content/public/browser/site_instance.h
@@ -140,14 +140,17 @@ class CONTENT_EXPORT SiteInstance : public base::RefCounted<SiteInstance> {
   // from scratch (or similar circumstances).
   //
   // The render process host factory may be nullptr.  See SiteInstance
-  // constructor.
+  // constructor.  |child_process_param_id| is an opaque id used passed to
+  // launch child processes.
   static scoped_refptr<SiteInstance> Create(
-      content::BrowserContext* browser_context);
+      content::BrowserContext* browser_context,
+      int child_process_param_id = 0);

[boliu, 2017/02/23 00:51:30]

I was wary to include child_process_launcher here to get the 0. Do you think
that include is fine? Or maybe DEFAULT_PARAM_ID should be declared here? Or
something else?

 
   // 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).
+  // to group chrome-ui pages into the same instance). Note
+  // |child_process_param_id| is not here purely because no caller uses it.
   static scoped_refptr<SiteInstance> CreateForURL(
       content::BrowserContext* browser_context,
       const GURL& url);