Add high dpi reference for extension icon on incognito tab.

BUG=129203
TEST=Run chrome with --force-device-scale-factor=2, open an incognito window, extension icon is sharp.


Review URL: https://chromiumcodereview.appspot.com/10828287

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151481 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/incognito_tab.css

@@ -38,6 +38,10 @@ html[dir='rtl'] .icon {
 }
 
 .extension-icon {
+  content: -webkit-image-set(
+      url('../../app/theme/default_100_percent/extensions_section.png') 1x,
+      url('../../app/theme/default_200_percent/extensions_section.png') 2x);
+  display: inline-block;
   left: 0;
   margin-top: -15px;
   position: absolute;

chrome/browser/resources/incognito_tab.html

@@ -16,7 +16,7 @@ document.write('<link id="incognitothemecss" rel="stylesheet" ' +
   <img src="shared/images/otr_icon_standalone.png" class="icon" />
   <span i18n-values=".innerHTML:content"></span>
   <div class="extensions-message">
-    <img src="../../app/theme/default_100_percent/extensions_section.png" class="extension-icon" />
+    <div class="extension-icon"></div>
     <span i18n-values=".innerHTML:extensionsmessage"></span>
   </div>
 </div>