aura: Clean up compositor initialization/destruction.

content/public/test/browser_test_base.cc

Index: content/public/test/browser_test_base.cc
diff --git a/content/public/test/browser_test_base.cc b/content/public/test/browser_test_base.cc
index d15e54bab0a7ea706f3ba46357a1cac339ad23ea..1ec65ec14b1c755d93bc91199af2e4ce0f8a9fc0 100644
--- a/content/public/test/browser_test_base.cc
+++ b/content/public/test/browser_test_base.cc
@@ -13,6 +13,7 @@
 #include "content/public/common/main_function_params.h"
 #include "content/public/test/test_utils.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
+#include "ui/compositor/compositor_switches.h"
 
 #if defined(OS_POSIX)
 #include "base/process/process_handle.h"
@@ -64,7 +65,8 @@ extern int BrowserMain(const MainFunctionParams&);
 BrowserTestBase::BrowserTestBase()
     : embedded_test_server_(
         new net::test_server::EmbeddedTestServer(
-            BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO))) {
+            BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO))),
+      allow_test_contexts_(true) {
 #if defined(OS_MACOSX)
   base::mac::SetOverrideAmIBundled(true);
   base::PowerMonitor::AllocateSystemIOPorts();
@@ -98,6 +100,14 @@ void BrowserTestBase::SetUp() {
       new base::Closure(
           base::Bind(&BrowserTestBase::ProxyRunTestOnMainThreadLoop, this));
 
+#if defined(USE_AURA)
+  // Copy what UITestBase::SetLaunchSwitches() does, and also what
+  // ChromeTestSuite does if the process had went into the test path. Otherwise
+  // tests will fail on bots.
+  if (allow_test_contexts_)
+    command_line->AppendSwitch(switches::kTestCompositor);
+#endif
+
   SetUpInProcessBrowserTestFixture();
 #if defined(OS_ANDROID)
   BrowserMainRunner::Create()->Initialize(params);