graphics_GLES2ConformChrome: better error reporting.

Tell the user that they have to run the test with internal Chrome
binaries.

BUG=chromium:392386
TEST=Ran with internal and external Chrome builds on link.

Change-Id: I78fc0e7981ab94fa1f7fb0303b3f51acb411435a
Reviewed-on: https://chromium-review.googlesource.com/207247
Tested-by: Ilja Friedel <ihf@chromium.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Commit-Queue: Ilja Friedel <ihf@chromium.org>
diff --git a/client/cros/chrome_binary_test.py b/client/cros/chrome_binary_test.py
index 41b8dfd..ac49f12 100755
--- a/client/cros/chrome_binary_test.py
+++ b/client/cros/chrome_binary_test.py
@@ -38,6 +38,10 @@
             shutil.rmtree(self.home_dir, ignore_errors=True)
 
 
+    def get_chrome_binary_path(self, binary_to_run):
+        return os.path.join(self.test_binary_dir, binary_to_run)
+
+
     def run_chrome_test_binary(self, binary_to_run, extra_params='', prefix='',
                                as_chronos=True):
         """
@@ -51,6 +55,7 @@
 
         @raises: error.TestFail if there is error running the command.
         """
+        binary = self.get_chrome_binary_path(binary_to_run)
         cmd = '%s/%s %s' % (self.test_binary_dir, binary_to_run, extra_params)
         env_vars = 'HOME=%s CR_SOURCE_ROOT=%s CHROME_DEVEL_SANDBOX=%s' % (
                 self.home_dir, self.cr_source_dir, self.CHROME_SANDBOX)