Make the dismiss button on the CF infobar be an image button.

chrome/app/chromium_strings.grd

Index: chrome/app/chromium_strings.grd
diff --git a/chrome/app/chromium_strings.grd b/chrome/app/chromium_strings.grd
index d409ab2c2e464c92c47924c15aa64d472c15a8a9..58408e7247e9ff698403ed005eff8c5cc00027ad 100644
--- a/chrome/app/chromium_strings.grd
+++ b/chrome/app/chromium_strings.grd
@@ -273,10 +273,10 @@ be available for now. -->
         </message>
         <message name="IDS_CHROME_FRAME_TURNDOWN_TEXT_IE_OLDER" desc="Text of Chromium Frame turndown prompt for IE 6, 7, and 8">
           This site is using the Chromium Frame plug-in which will soon be unsupported. Please uninstall it and upgrade to a modern browser.
-	</message>
+        </message>
         <message name="IDS_CHROME_FRAME_TURNDOWN_TEXT_IE_NEWER" desc="Text of Chromium Frame turndown prompt for IE 9 and 10">
           This site is using the Chromium Frame plug-in that will soon be unsupported. Please uninstall it and download a compatible browser.
-	</message>
+        </message>
         <message name="IDS_SHORTCUT_NEW_WINDOW" desc="The text label of the New window shortcut context menu entry as of Windows 8">
           New window
         </message>