Coverity: Fix several pass-by-values.

chrome/browser/themes/browser_theme_pack.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/themes/browser_theme_pack.h"
 
 #include <limits>
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 359 matching lines @@
       &pack->prepared_images_);
 
   pack->GenerateTabBackgroundImages(&pack->prepared_images_);
 
   // The BrowserThemePack is now in a consistent state.
   return pack;
 }
 
 // static
 scoped_refptr<BrowserThemePack> BrowserThemePack::BuildFromDataPack(
-    FilePath path, const std::string& expected_id) {
+    const FilePath& path, const std::string& expected_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   // Allow IO on UI thread due to deep-seated theme design issues.
   // (see http://crbug.com/80206)
   base::ThreadRestrictions::ScopedAllowIO allow_io;
   scoped_refptr<BrowserThemePack> pack(new BrowserThemePack);
   pack->data_pack_.reset(
       new ui::DataPack(ui::SCALE_FACTOR_100P));
 
   if (!pack->data_pack_->LoadFromPath(path)) {
     LOG(ERROR) << "Failed to load theme data pack.";
@@ skipping 687 matching lines @@
         hsl.h = tints_[i].h;
         hsl.s = tints_[i].s;
         hsl.l = tints_[i].l;
         return hsl;
       }
     }
   }
 
   return ThemeService::GetDefaultTint(id);
 }