Use stub GL draw/clear calls for browser tests that do not need pixels.

chrome/test/ppapi/ppapi_test.cc

Index: chrome/test/ppapi/ppapi_test.cc
diff --git a/chrome/test/ppapi/ppapi_test.cc b/chrome/test/ppapi/ppapi_test.cc
index b21dc9cc9c8f4c372e9b608180ca2e1f8939da94..84b00a5360d53b06f60921fea59912e2cc77a2fb 100644
--- a/chrome/test/ppapi/ppapi_test.cc
+++ b/chrome/test/ppapi/ppapi_test.cc
@@ -129,6 +129,13 @@ void PPAPITestBase::InfoBarObserver::VerifyInfoBarState() {
 PPAPITestBase::PPAPITestBase() {
 }
 
+void PPAPITestBase::SetUp() {
+  // Some of these tests require pixel output.
+  UseRealGLContexts();
+
+  InProcessBrowserTest::SetUp();
+}
+
 void PPAPITestBase::SetUpCommandLine(CommandLine* command_line) {
   // The test sends us the result via a cookie.
   command_line->AppendSwitch(switches::kEnableFileCookies);