Revert of base: Remove using:: declaration from version.h header.

chrome/browser/extensions/webstore_installer.cc

Index: chrome/browser/extensions/webstore_installer.cc
diff --git a/chrome/browser/extensions/webstore_installer.cc b/chrome/browser/extensions/webstore_installer.cc
index 53ce4dd5e34386e32223e697f49736d4e7f2d12e..6ab5475321b80b78b06a110033e03dd770168ce5 100644
--- a/chrome/browser/extensions/webstore_installer.cc
+++ b/chrome/browser/extensions/webstore_installer.cc
@@ -418,7 +418,7 @@
     CHECK_EQ(extension->id(), id_);
     ReportSuccess();
   } else {
-    const base::Version version_required(info.minimum_version);
+    const Version version_required(info.minimum_version);
     if (version_required.IsValid() &&
         extension->version()->CompareTo(version_required) < 0) {
       // It should not happen, CrxInstaller will make sure the version is
@@ -490,10 +490,11 @@
     scoped_ptr<Approval> approval = Approval::CreateForSharedModule(profile_);
     const SharedModuleInfo::ImportInfo& info = pending_modules_.front();
     approval->extension_id = info.extension_id;
-    const base::Version version_required(info.minimum_version);
+    const Version version_required(info.minimum_version);
 
     if (version_required.IsValid()) {
-      approval->minimum_version.reset(new base::Version(version_required));
+      approval->minimum_version.reset(
+          new Version(version_required));
     }
     download_item_->SetUserData(kApprovalKey, approval.release());
   } else {