PlzNavigate: Speculatively spawns a renderer process for navigations.

content/test/test_web_contents.h

Index: content/test/test_web_contents.h
diff --git a/content/test/test_web_contents.h b/content/test/test_web_contents.h
index 8e3c2b55f382e97046ed300a1fbcd5cd4df6e19a..886e337e1a18a65e3a9ab67cf72e9bd3fe9d1341 100644
--- a/content/test/test_web_contents.h
+++ b/content/test/test_web_contents.h
@@ -94,6 +94,13 @@ class TestWebContents : public WebContentsImpl, public WebContentsTester {
                                 int error_code,
                                 const base::string16& error_description);
 
+  // PlzNavigate
+  // When running in regular mode returns the same result as a call to
+  // GetPendingMainFrame. When browser side navigation is enabled it returns the
+  // speculative RenderFrameHost for the main frame if one exists. Otherwise
+  // returns nullptr.
+  TestRenderFrameHost* GetNextMainFrameCandidate() const;

[Charlie Reis, 2015/01/12 23:30:53]

It seems a bit awkward to have this, especially since it's not listed near
GetPendingMainFrame.

We should either make GetPendingMainFrame behave this way (i.e., return the
speculative RFH in PlzNavigate mode) or make the caller do the check.  Since
there's only one caller so far, I'm inclined to do the latter.

[carlosk, 2015/01/13 15:54:13]

This was meant to help with the efforts of making tests pass with PlzNavigate
enabled. We didn't consider the option of changing the behavior of
GetPendingMainFrame as it might look inconsistent. But as you are OK with that
it's certainly the easiest choice for us as we won't need to replace all of its
occurrences in the future. 

Updated GetPendingMainFrame, removed GetNextMainFrameCandidate and updated the
doc comment for GetPendingMainFrame in web_contents_tester.h.

+
  protected:
   // The deprecated WebContentsTester still needs to subclass this.
   explicit TestWebContents(BrowserContext* browser_context);