PlzNavigate: Avoid duplicate SiteInstance creation during navigation.

content/browser/frame_host/render_frame_host_manager.h

Index: content/browser/frame_host/render_frame_host_manager.h
diff --git a/content/browser/frame_host/render_frame_host_manager.h b/content/browser/frame_host/render_frame_host_manager.h
index f7c15e2bc63fbb2a350fbb1981a4dac184927def..4ac6e3f737cf192d5508e9d5457b2541a6fbdf9a 100644
--- a/content/browser/frame_host/render_frame_host_manager.h
+++ b/content/browser/frame_host/render_frame_host_manager.h
@@ -425,6 +425,36 @@ class CONTENT_EXPORT RenderFrameHostManager : public NotificationObserver {
   FRIEND_TEST_ALL_PREFIXES(CrossProcessFrameTreeBrowserTest,
                            CreateCrossProcessSubframeProxies);
 
+  // PlzNavigate
+  enum RenderFrameHostToUse {
+    INVALID,
+    REUSE_CURRENT,
+    NEW_SPECULATIVE,
+    REUSE_SPECULATIVE,
+  };
+
+  // Stores information regarding a SiteInstance targeted at a specific URL. It
+  // can whether point to an existent one or store the details needed to create

[Charlie Reis, 2015/03/25 00:09:25]

nit: can point (drop "whether")

s/existent/existing/ (everywhere)

[carlosk, 2015/03/30 14:37:38]

Done.

+  // a new one.
+  struct SiteInstanceDescriptor {
+    explicit SiteInstanceDescriptor(content::SiteInstance* site_instance)
+        : existent_site_instance(site_instance),
+          new_site_is_related_to_current(false) {}
+
+    SiteInstanceDescriptor(GURL site_url, bool related_to_current)
+        : existent_site_instance(nullptr),
+          new_site_url(site_url),
+          new_site_is_related_to_current(related_to_current) {}
+
+    // Set with an existent SiteInstance to be reused.
+    content::SiteInstance* existent_site_instance;
+    // In case |existent_site_instance| is null, specify a new site URL.
+    GURL new_site_url;
+    // In case |existent_site_instance| is null, specify if the new site should
+    // be created in new BrowsingInstance or not.
+    bool new_site_is_related_to_current;

[Charlie Reis, 2015/03/25 00:09:26]

"site" doesn't fit well in this name.  This descriptor is about SiteInstances,
not sites.

Let's call this new_is_related_to_current instead.  In that sense,
"new_site_url" means "the site URL for the new SiteInstance" and
"new_is_related_to_current" means "the new SiteInstance is related to the
current SiteInstance."

[carlosk, 2015/03/30 14:37:38]

Done.

+  };
+
   // Used with FrameTree::ForEach to erase RenderFrameProxyHosts from a
   // FrameTreeNode's RenderFrameHostManager.
   static bool ClearProxiesInSiteInstance(int32 site_instance_id,
@@ -473,29 +503,46 @@ class CONTENT_EXPORT RenderFrameHostManager : public NotificationObserver {
   SiteInstance* GetSiteInstanceForNavigation(const GURL& dest_url,
                                              SiteInstance* source_instance,
                                              SiteInstance* dest_instance,
+                                             SiteInstance* candidate_instance,
                                              ui::PageTransition transition,
                                              bool dest_is_restore,
                                              bool dest_is_view_source_mode);
 
-  // Returns an appropriate SiteInstance object for the given |dest_url|,
-  // possibly reusing the current SiteInstance.  If --process-per-tab is used,
-  // this is only called when ShouldSwapBrowsingInstancesForNavigation returns
-  // true. |source_instance| is the SiteInstance of the frame that initiated the
-  // navigation. |current_instance| is the SiteInstance of the frame that is
-  // currently navigating. |dest_instance|, is a predetermined SiteInstance
-  // that'll be used if not null.
+  // PlzNavigate
+  // Returns true if |candidate_instance| confirms to the SiteInstance specified

[Charlie Reis, 2015/03/25 00:09:25]

"confirms to" isn't grammatically correct.  "matches" would work.

[carlosk, 2015/03/30 14:37:38]

It was a typo: I meant to write "conforms". But "matches" sounds good as well.
Done.

+  // by |descriptor|.
+  bool SiteInstanceMatchesDescription(SiteInstance* candidate_instance,

[carlosk, 2015/03/24 15:30:06]

I wanted to move this method into an unnamed namespace but it would require
un-privatizing SiteInstanceDescriptor. So... WDYT?

[Charlie Reis, 2015/03/25 00:09:25]

Please keep SiteInstanceDescriptor private.

[carlosk, 2015/03/30 14:37:38]

Acknowledged.

+                                      const SiteInstanceDescriptor& descriptor);
+
+  // Returns a descriptor of the appropriate SiteInstance object for the given
+  // |dest_url|, possibly reusing the current, source or destination
+  // SiteInstance. It will check ShouldTransitionCrossSite and

[Charlie Reis, 2015/03/25 00:09:25]

This second sentence is an implementation detail and isn't needed here anymore.

[carlosk, 2015/03/30 14:37:38]

Done.

+  // ShouldSwapBrowsingInstancesForNavigation.
+  // |source_instance| is the SiteInstance of the frame that initiated the

[Charlie Reis, 2015/03/25 00:09:25]

nit: Add an empty comment line above this.

[carlosk, 2015/03/30 14:37:38]

Done.

+  // navigation. |dest_instance|, is a predetermined SiteInstance

[Charlie Reis, 2015/03/25 00:09:25]

Remove comma.

[carlosk, 2015/03/30 14:37:38]

Done.

+  // that'll be used if not null. Internally, |current_instance| is the

[Charlie Reis, 2015/03/25 00:09:25]

that'll -> that will

[carlosk, 2015/03/30 14:37:38]

Done.

+  // SiteInstance of the frame that is currently navigating.
   // For example, if you have a parent frame A, which has a child frame B, and
   // A is trying to change the src attribute of B, this will cause a navigation
   // where the source SiteInstance is A and B is the current SiteInstance.
-  // This is a helper function for GetSiteInstanceForNavigation.
-  SiteInstance* GetSiteInstanceForURL(const GURL& dest_url,
-                                      SiteInstance* source_instance,
-                                      SiteInstance* current_instance,
-                                      SiteInstance* dest_instance,
-                                      ui::PageTransition transition,
-                                      bool dest_is_restore,
-                                      bool dest_is_view_source_mode,
-                                      bool force_browsing_instance_swap);
+  // This is a helper function for GetSiteInstanceForNavigation and

[Charlie Reis, 2015/03/25 00:09:26]

nit: Add an empty comment line above this.

[carlosk, 2015/03/30 14:37:38]

Done.

+  // IsCorrectSiteInstanceForURL.
+  SiteInstanceDescriptor DetermineSiteInstanceForURL(
+      const GURL& dest_url,
+      SiteInstance* source_instance,
+      SiteInstance* dest_instance,
+      ui::PageTransition transition,
+      bool dest_is_restore,
+      bool dest_is_view_source_mode);
+  SiteInstanceDescriptor DetermineSiteInstanceForURLInternal(

[Charlie Reis, 2015/03/25 00:09:25]

These functions are already private internal details.  Please just have the
latter one and drop the word "Internal" from the name.

[carlosk, 2015/03/30 14:37:38]

I explained this here:
https://codereview.chromium.org/967383002/diff/80001/content/browser/frame_ho...

But following the suggestion from another comment the *Internal version was in
fact eliminated.

+      const GURL& dest_url,
+      SiteInstance* source_instance,
+      SiteInstance* current_instance,
+      SiteInstance* dest_instance,
+      ui::PageTransition transition,
+      bool dest_is_restore,
+      bool dest_is_view_source_mode,
+      bool force_browsing_instance_swap);
 
   // Determines the appropriate url to use as the current url for SiteInstance
   // selection.