Makes tests either use mock compositor or mock WebGraphicsContext3D

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index bf4e4ab36bdbc0196142b4b2080ef362f1723014..f82a071fd44ba6e238261fa8cab86748035161d2 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1287,6 +1287,11 @@ const char kEnablePrintPreview[]            = "enable-print-preview";
 // Enables the benchmarking extensions.
 const char kEnableBenchmarking[]            = "enable-benchmarking";
 
+#if defined(USE_AURA)
+// Forces usage of the test compositor. Needed to run ui tests on bots.
+extern const char kTestCompositor[]         = "test-compositor";
+#endif
+
 bool IsPrintPreviewEnabled() {
   if (CommandLine::ForCurrentProcess()->HasSwitch(kDisablePrintPreview))
     return false;