Add test coverage for --prerender=disabled switch

chrome/browser/prerender/prerender_unittest.cc

Index: chrome/browser/prerender/prerender_unittest.cc
diff --git a/chrome/browser/prerender/prerender_unittest.cc b/chrome/browser/prerender/prerender_unittest.cc
index ea4a53de267de1372fae2b6f7894690a4ff00879..78227a3d91f3dda16c46f1f49e46232b31594fef 100644
--- a/chrome/browser/prerender/prerender_unittest.cc
+++ b/chrome/browser/prerender/prerender_unittest.cc
@@ -15,6 +15,7 @@
 #include "base/time/time.h"
 #include "chrome/browser/net/prediction_options.h"
 #include "chrome/browser/prerender/prerender_contents.h"
+#include "chrome/browser/prerender/prerender_field_trial.h"
 #include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_link_manager.h"
 #include "chrome/browser/prerender/prerender_manager.h"
@@ -405,6 +406,16 @@ class PrerenderTest : public testing::Test {
   base::FieldTrialList field_trial_list_;
 };
 
+TEST_F(PrerenderTest, PrerenderRespectsDisableFlag) {
+  ASSERT_TRUE(PrerenderManager::IsPrerenderingPossible());
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  command_line->AppendSwitchASCII(
+    switches::kPrerenderMode,
+    switches::kPrerenderModeSwitchValueDisabled);
+  prerender::ConfigurePrerender(*command_line);
+  ASSERT_FALSE(PrerenderManager::IsPrerenderingPossible());
+}
+
 TEST_F(PrerenderTest, FoundTest) {
   GURL url("http://www.google.com/");
   DummyPrerenderContents* prerender_contents =