Remove //chrome dependency from ExtensionPrefs

chrome/browser/extensions/chrome_extensions_browser_client.h

Index: chrome/browser/extensions/chrome_extensions_browser_client.h
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.h b/chrome/browser/extensions/chrome_extensions_browser_client.h
index dd2d46948e0bae7d81ba1993435a1238a9f85980..cdae597d5aff103e7ec667477e15dfda2dd47dfc 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.h
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.h
@@ -23,6 +23,7 @@ class BrowserContext;
 namespace extensions {
 
 class ChromeExtensionsAPIClient;
+class ContentSettingsPrefsObserver;
 
 // Implementation of extensions::BrowserClient for Chrome, which includes
 // knowledge of Profiles, BrowserContexts and incognito.
@@ -57,6 +58,9 @@ class ChromeExtensionsBrowserClient : public ExtensionsBrowserClient {
       content::BrowserContext* context) const OVERRIDE;
   virtual PrefService* GetPrefServiceForContext(
       content::BrowserContext* context) OVERRIDE;
+  virtual void GetAdditionalExtensionPrefsObservers(
+      content::BrowserContext* context,
+      std::vector<ExtensionPrefs::Observer*>* observers) const OVERRIDE;
   virtual bool DeferLoadingBackgroundHosts(
       content::BrowserContext* context) const OVERRIDE;
   virtual bool IsBackgroundPageAllowed(