Allow use of EGL in browser tests with --use-gl=egl.

ui/gl/gl_switches.cc

Index: ui/gl/gl_switches.cc
diff --git a/ui/gl/gl_switches.cc b/ui/gl/gl_switches.cc
index d32786fd43c0be436455d38fb8488e93427ece38..99971364012c53f43c390aaf4608069a02e40950 100644
--- a/ui/gl/gl_switches.cc
+++ b/ui/gl/gl_switches.cc
@@ -60,12 +60,16 @@ const char kGpuSwitchingOptionNameForceDiscrete[]   = "force_discrete";
 // library first, but fall back to regular library if loading fails.
 const char kTestGLLib[]                     = "test-gl-lib";
 
+// Use hardware gpu, if available, for tests.
+const char kUseGpuInTests[] = "use-gpu-in-tests";
+
 // Disables GL drawing operations which produce pixel output. With this
 // the GL output will not be correct but tests will run faster.
 const char kDisableGLDrawingForTests[] = "disable-gl-drawing-for-tests";
 
-// Use hardware gpu, if available, for tests.
-const char kUseGpuInTests[] = "use-gpu-in-tests";
+// Forces the use of OSMesa instead of hardware gpu.
+const char kOverrideUseGLWithOSMesaForTests[] =
+    "override-use-gl-with-osmesa-for-tests";
 
 // This is the list of switches passed from this file that are passed from the
 // GpuProcessHost to the GPU Process. Add your switch to this list if you need