Instant: Use only one hidden WebContents per profile.

chrome/browser/instant/instant_service_observer.h

Index: chrome/browser/instant/instant_service_observer.h
diff --git a/chrome/browser/instant/instant_service_observer.h b/chrome/browser/instant/instant_service_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..a90e114ad7e65d2dd4bd05be7e869d289ea2a99a
--- /dev/null
+++ b/chrome/browser/instant/instant_service_observer.h
@@ -0,0 +1,22 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_
+#define CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_
+
+// This class defines the observer interface for InstantService.
+class InstantServiceObserver {
+ public:
+  virtual void InstantStatusChanged() = 0;

[samarth, 2013/03/01 17:59:53]

Please document each of these.

[sreeram, 2013/03/07 18:18:46]

Done.

+  virtual void ThemeInfoChanged() = 0;
+  virtual void MostVisitedItemsChanged() = 0;
+
+  // For use in tests only.

[samarth, 2013/03/01 17:59:53]

I've seen an #ifdef UNIT_TEST in other places.  Is there a #ifdef TEST or
something that works for browser tests too that we can use here to enforce this?

[sreeram, 2013/03/07 18:18:46]

Done. Took this out. It was a bad idea to force regular objects
(InstantControllerImpl and InstantPreloader) to implement this
meant-for-tests-only interface. Instead, we now use a notification.

Aside: #define UNIT_TEST works for browser tests too, despite its name. However,
I couldn't have used it here. The macro is set when compiling any test .cc file,
but since instant_service.cc would've referenced this method, it wouldn't have
worked. I.e., when instant_service.cc is compiled, the macro is false, so fine,
all references to InstantSupportDecided() vanish. But now, you compile a
*-test.cc file, and sure, it defines the macro, so you happily wait for
InstantSupportDecided() to be called. Now, instant_service.cc is NOT going to be
recompiled just to link your unit_test, so the call never arrives.

+  virtual void InstantSupportDecided() = 0;
+
+ protected:
+  ~InstantServiceObserver() {}
+};
+
+#endif  // CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_