Refactor Extension initialization logic. Add tracing and additional histogram.

chrome/browser/extensions/installed_loader.h

Index: chrome/browser/extensions/installed_loader.h
diff --git a/chrome/browser/extensions/installed_loader.h b/chrome/browser/extensions/installed_loader.h
index a9b50017490781f189d30efa9ad0505e947555f1..8d8ec7f166e2c6e71bedb26cefb259a5a5705804 100644
--- a/chrome/browser/extensions/installed_loader.h
+++ b/chrome/browser/extensions/installed_loader.h
@@ -30,6 +30,9 @@ class InstalledLoader {
   // extension that is already installed.
   int GetCreationFlags(const ExtensionInfo* info);
 
+  // Record metrics related to the loaded extensions.
+  void RecordExtensionsMetrics();
+
   ExtensionService* extension_service_;
   ExtensionRegistry* extension_registry_;