Consistently use namespaced base::Version in extensions code.

chrome/browser/extensions/pending_extension_info.h

Index: chrome/browser/extensions/pending_extension_info.h
diff --git a/chrome/browser/extensions/pending_extension_info.h b/chrome/browser/extensions/pending_extension_info.h
index 9d4e939180e34a55fbb5592cef1260f760f6fd68..7eb6feb47051d4fa903add834106fc3140e11af8 100644
--- a/chrome/browser/extensions/pending_extension_info.h
+++ b/chrome/browser/extensions/pending_extension_info.h
@@ -30,7 +30,7 @@ class PendingExtensionInfo {
   PendingExtensionInfo(const std::string& id,
                        const std::string& install_parameter,
                        const GURL& update_url,
-                       const Version& version,
+                       const base::Version& version,
                        ShouldAllowInstallPredicate should_allow_install,
                        bool is_from_sync,
                        Manifest::Location install_source,
@@ -50,7 +50,7 @@ class PendingExtensionInfo {
 
   const std::string& id() const { return id_; }
   const GURL& update_url() const { return update_url_; }
-  const Version& version() const { return version_; }
+  const base::Version& version() const { return version_; }
   const std::string& install_parameter() const { return install_parameter_; }
 
   // ShouldAllowInstall() returns the result of running constructor argument
@@ -79,7 +79,7 @@ class PendingExtensionInfo {
   std::string id_;
 
   GURL update_url_;
-  Version version_;
+  base::Version version_;
   std::string install_parameter_;
 
   // When the extension is about to be installed, this function is