Don't create unnecessary OOPIFs for subframe navigations that don't require a dedicated process.

chrome/browser/extensions/process_manager_browsertest.cc

Index: chrome/browser/extensions/process_manager_browsertest.cc
diff --git a/chrome/browser/extensions/process_manager_browsertest.cc b/chrome/browser/extensions/process_manager_browsertest.cc
index adaf411010263d70ef6491d0d12833856fa99f96..e7022f06e2cc2280670ba217982ce1157f3df1e4 100644
--- a/chrome/browser/extensions/process_manager_browsertest.cc
+++ b/chrome/browser/extensions/process_manager_browsertest.cc
@@ -1220,4 +1220,55 @@ IN_PROC_BROWSER_TEST_F(ProcessManagerBrowserTest,
   VerifyPostMessageToOpener(popup->GetMainFrame(), extension_frame);
 }
 
+// Test that when a web site has an extension iframe, navigating that iframe to
+// a different web site without --site-per-process will place it in the parent
+// frame's process.  See https://crbug.com/711006.
+IN_PROC_BROWSER_TEST_F(ProcessManagerBrowserTest,
+                       ExtensionFrameNavigatesToParentSiteInstance) {
+  // This test matters only *without* --site-per-process.
+  if (content::AreAllSitesIsolatedForTesting())

[Devlin, 2017/04/17 21:49:32]

Would it be worth enforcing this in the test via SetUpCommandLine or similar? 
Trybots have a funny way of usually running with all the experiments turned on.

[alexmos, 2017/04/17 22:38:59]

Good idea, but it might be tricky.  I don't see an easy way to remove a switch
when it's already been added (e.g., on bots that run with --site-per-process). 
It also might be dangerous to do it here inside the test, as we might've already
started making some process model assumptions (e.g.,
BrowserProcessImpl::PreCreateThreads has checks for --isolate-extensions).

I think it's pretty safe to assume that we'll have bots running tests without
--site-per-process for the time being, and we have other tests that rely on
this.  If we ever end up in our dream world of --site-per-process being on by
default, we'll probably want to do something uniformly for all our tests that do
this kind of thing.

[Devlin, 2017/04/17 23:03:37]

Fair enough, but my $0.02 are that it's worth looking into sooner rather than
later.  I've been bit multiple times because of bot configurations.

But, certainly doesn't need to block this CL. :)

[alexmos, 2017/04/17 23:07:58]

Acknowledged, we probably should discuss bot configurations/coverage some time
soon given all the different OOPIF modes we're working on, so I'll bring this
up.

+    return;
+
+  host_resolver()->AddRule("*", "127.0.0.1");
+
+  // Create a simple extension without a background page.
+  const Extension* extension = CreateExtension("Extension", false);
+  embedded_test_server()->ServeFilesFromDirectory(extension->path());
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  // Navigate main tab to a web page with a blank iframe.  There should be no
+  // extension frames yet.
+  NavigateToURL(embedded_test_server()->GetURL("a.com", "/blank_iframe.html"));
+  ProcessManager* pm = ProcessManager::Get(profile());
+  EXPECT_EQ(0u, pm->GetAllFrames().size());
+  EXPECT_EQ(0u, pm->GetRenderFrameHostsForExtension(extension->id()).size());
+
+  content::WebContents* tab =
+      browser()->tab_strip_model()->GetActiveWebContents();
+
+  // Navigate subframe to an extension URL.  This should go into a new
+  // extension process.
+  const GURL extension_url(extension->url().Resolve("empty.html"));
+  EXPECT_TRUE(content::NavigateIframeToURL(tab, "frame0", extension_url));
+  EXPECT_EQ(1u, pm->GetRenderFrameHostsForExtension(extension->id()).size());
+  EXPECT_EQ(1u, pm->GetAllFrames().size());
+
+  content::RenderFrameHost* main_frame = tab->GetMainFrame();
+  {
+    content::RenderFrameHost* subframe = ChildFrameAt(main_frame, 0);
+    EXPECT_NE(subframe->GetProcess(), main_frame->GetProcess());
+    EXPECT_NE(subframe->GetSiteInstance(), main_frame->GetSiteInstance());
+  }
+
+  // Navigate subframe to b.com.  This should be brought back to the parent
+  // frame's (a.com) process.
+  GURL b_url(embedded_test_server()->GetURL("b.com", "/empty.html"));
+  EXPECT_TRUE(content::NavigateIframeToURL(tab, "frame0", b_url));
+  {
+    content::RenderFrameHost* subframe = ChildFrameAt(main_frame, 0);
+    EXPECT_EQ(subframe->GetProcess(), main_frame->GetProcess());
+    EXPECT_EQ(subframe->GetSiteInstance(), main_frame->GetSiteInstance());
+  }
+}
+
 }  // namespace extensions