Modified comment in PlatformAppBrowserTest.WindowDotPrintWorks.

The PlatformAppBrowserTest.WindowDotPrintWorks test will only run
automatically for Chrome branded builds because it requires the PDF
plug-in, which isn't provided for Chromium builds. It can be run
manually for Chromium builds, however, and this change expands the
comment explaining how to do this on Linux to add an explanation of
how to do this on OS X.

TBR=asargent@chromium.org
BUG=none

Review URL: https://chromiumcodereview.appspot.com/23708018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@222228 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/apps/app_browsertest.cc

@@ -1044,9 +1044,12 @@ IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, MAYBE_WebContentsHasFocus) {
 //   1) Remove "MAYBE_" in the first line of the test definition
 //   2) Build Chromium browser_tests
 //   3) Make a copy of the PDF plug-in from a recent version of Chrome (Canary
-//      or recent development build) to your Chromium build. On Linux and Chrome
-//      OS, this just involves copying /opt/google.chrome/libpdf.so to
-//      <path-to-your-src>/out/Debug.
+//      or a recent development build) to your Chromium build:
+//      - On Linux and Chrome OS, copy /opt/google.chrome/libpdf.so to
+//        <path-to-your-src>/out/Debug
+//      - On OS X, copy PDF.plugin from
+//        <recent-chrome-app-folder>/*/*/*/*/"Internet Plug-Ins" to
+//        <path-to-your-src>/out/Debug/Chromium.app/*/*/*/*/"Internet Plug-Ins"
 //   4) Run browser_tests with the --enable-print-preview flag
 
 #if !defined(GOOGLE_CHROME_BUILD)